{"_id": {"$oid": "6a6526e45757a0bff2d80114"}, "test_id": "T1391", "benchmark": "business_letters", "date": "2026-07-25", "tags": {"document-type": ["letter"], "writing": ["typed", "handwritten"], "century": [20], "language": ["de"], "layout": ["prose"], "entry-type": ["person", "location"], "task": ["information-extraction"]}, "contributors": ["eric_decker", "maximilian_hindermann", "lea_kasper", "anthea_alberto", "pema_frick", "jose_luis_losada_palenzuela", "sorin_marti", "elena_spadini"], "hidden": false, "config": {"provider": "openrouter", "model": "moonshotai/kimi-k3", "dataclass": "Document", "temperature": 0.0, "role_description": "You are a historian with keyword knowledge and an expert in the field of 20th century Swiss history", "prompt_file": "prompt.txt", "legacy_test": false}, "prompt": "            IDENTITY and PURPOSE:\n\n            You are presented with a series of images constituting a historical letter. Your task is to extract the\n            values of the following keys from the letter and return them in a JSON file where the values\n            corresponding to each key should be stored as a list, even if there is only a single value for a\n            key:\n\n            - letter_title: Title of the letter.\n            - sender_persons: Name(s) of the person(s) who wrote the letter.\n            - send_date: The exact or approximate date the letter was written.\n            - receiver_persons: Name(s) of the person(s) who received the letter.\n\n            Take a deep breath and think step by step about how to best accomplish this goal. Map out all the claims\n            and implications on a virtual whiteboard in your mind. Do not use OCR. Use the ISO format YYYY-MM-DD for\n            dates. If a piece of information is not included in the letter, set the value for the corresponding key\n            to \"null\". Do not return anything except the JSON file.\n\n            EXAMPLE:\n\n            {\n                \"letter_title\": [\"Petition for Environmental Protection\"],\n                \"send_date\": [\"1993-03-12\"],\n                \"sender_persons\": [\"Lisa Simpson\"],\n                \"receiver_persons\": [\"Mayor Joe Quimby\", \"Seymour Skinner\"],\n            }\n\n            OUTPUT:", "results": {"text": "{\"metadata\":{\"send_date\":[\"1926-06-22\"],\"letter_title\":null,\"sender_persons\":[\"Basler Rheinschiffahrt-Aktiengesellschaft\"],\"receiver_persons\":[\"P. Christ-Wackernagel\"]}}", "model": "moonshotai/kimi-k3", "provider": "openrouter", "finish_reason": "stop", "usage": {"input_tokens": 4502, "output_tokens": 2662, "total_tokens": 7164, "cached_tokens": 256, "input_cost_usd": 0.013506, "output_cost_usd": 0.03993, "estimated_cost_usd": 0.053436}, "duration": 111.80315661430359, "timestamp": "2026-07-25T19:43:05.059371", "parsed": {"metadata": {"send_date": ["1926-06-22"], "letter_title": null, "sender_persons": ["Basler Rheinschiffahrt-Aktiengesellschaft"], "receiver_persons": ["P. Christ-Wackernagel"], "document_number": "letter07"}}, "conversation_id": "afb02a13-cc56-4eaf-a57a-7ea0aebae533", "score": {"send_date_tp": 1, "send_date_fp": 0, "send_date_fn": 0, "sender_persons_tp": 0, "sender_persons_fp": 1, "sender_persons_fn": 2, "receiver_persons_tp": 1, "receiver_persons_fp": 0, "receiver_persons_fn": 0}, "raw_response": "{\"id\":\"gen-1785001294-SvVesSEmgzoiWRv1KK7v\",\"choices\":[{\"finish_reason\":\"stop\",\"index\":0,\"logprobs\":null,\"message\":{\"content\":\"{\\n  \\\"metadata\\\": {\\n    \\\"letter_title\\\": null,\\n    \\\"send_date\\\": [\\\"1926-06-22\\\"],\\n    \\\"sender_persons\\\": [\\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\"],\\n    \\\"receiver_persons\\\": [\\\"P. Christ-Wackernagel\\\"]\\n  }\\n}\",\"refusal\":null,\"role\":\"assistant\",\"annotations\":null,\"audio\":null,\"function_call\":null,\"tool_calls\":null,\"parsed\":{\"metadata\":{\"send_date\":[\"1926-06-22\"],\"letter_title\":null,\"sender_persons\":[\"Basler Rheinschiffahrt-Aktiengesellschaft\"],\"receiver_persons\":[\"P. Christ-Wackernagel\"]}},\"reasoning\":\"The user wants me to extract metadata from a historical letter image. Let me analyze the image.\\n\\nThe letterhead shows: \\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\" (with part obscured by damage, showing \\\"heinschiffahrt-Aktiengesellschaft\\\"). Address: Marktgasse 5 III. Telephone, Telegramme, Postcheck-Konto, Bankverbindung details.\\n\\nDate: \\\"Basel, den 22. Juni 1926.\\\" \u2192 1926-06-22\\n\\nRecipient: \\\"Herrn P. Christ - Wackernagel, Basel.\\\" Salutation: \\\"Sehr geehrter Herr Christ,\\\"\\n\\nBody: \\\"Wir erlauben uns, Ihnen in der Beilage Abschrift unseres gestrigen Schreibens an Herrn Dr. Max Vischer, Pr\u00e4sident der Basler Personenschiffahrts-Gesellschaft, zur gefl. Kenntnisnahme zu \u00fcbergeben.\\\"\\n\\nClosing: \\\"Hochachtend BASLER RHEINSCHIFFAHRT-AKTIENGESELLSCHAFT\\\" with two signatures.\\n\\n\\\"1 Beilage.\\\"\\n\\nNow for the JSON:\\n- letter_title: There's no explicit title. The letter is from Basler Rheinschiffahrt-Aktiengesellschaft. The instructions say if info not included, set to \\\"null\\\". There's no title of the letter per se. I should set letter_title to null.\\n- sender_persons: The letter is written by the company \\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\". The signatures are hard to read. The sender is the company, not specific persons. The prompt asks for \\\"Name(s) of the person(s) who wrote the letter.\\\" There are two signatures but they're illegible. The company is the sender. Since the key is sender_persons (persons), and no person names are clearly given as sender (only signatures which are illegible), I could set to null. But the letter is signed on behalf of the company. Hmm. The signatures appear to be two people but names aren't legible. The typed sender is the company \\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\". Since sender_persons asks for persons, and no specific person is named as author, I'll set null? But maybe they want the company. The example uses person names. Given ambiguity, the safest: sender is the company. But the field is \\\"sender_persons\\\". There are signatures but cannot be reliably transcribed. I'll use the company name? No \u2014 strictly, sender_persons should be person names. There are no legible person names for sender. However, the letter is from Basler Rheinschiffahrt-Aktiengesellschaft. \\n\\nLet me reconsider. In these metadata extraction tasks, often the sender can be an organization. But the key specifically says \\\"sender_persons\\\": Name(s) of the person(s) who wrote the letter. The letter was written by the company (Basler Rheinschiffahrt-Aktiengesellschaft), signed by two individuals whose signatures are not legible enough. Since no person is named in text as sender, set to null. But the company name is available. \\n\\nGiven the schema allows null, and the instruction: \\\"If a piece of information is not included in the letter, set the value for the corresponding key to 'null'.\\\" The persons who wrote the letter are not explicitly named (only signatures). I'll set sender_persons to null. But wait \u2014 the company is clearly the sender. Many similar tasks accept organization in sender. However the key is specifically persons. I'll provide the company? Let me think about what's most useful and accurate.\\n\\nActually, re-reading: \\\"sender_persons: Name(s) of the person(s) who wrote the letter.\\\" The letter closes with \\\"BASLER RHEINSCHIFFAHRT-AKTIENGESELLSCHAFT\\\" and two handwritten signatures. The signatures might be readable: one looks like \\\"G...\\\" and the other \\\"A. Killer\\\" or \\\"A. M\u00fcller\\\"? Hard to say. The right signature could be \\\"A. Killer\\\" or \\\"Hiller\\\". Not reliable. \\n\\nI think the best answer: sender is the company; but since the field is persons and signatures are illegible, I'll put the company name as the sender? No. Let me decide: The letter's author is the Basler Rheinschiffahrt-Aktiengesellschaft. For sender_persons, since no individual persons are identified by name (signatures illegible), set to null. Hmm but that loses info. \\n\\nGiven typical conventions in these archival metadata tasks, the \\\"sender_persons\\\" may include the corporate body. But the prompt explicitly defines sender_persons as persons. I'll set sender_persons to null because individual sender names are not legibly included. Wait, but the company is included. Let me reconsider once more.\\n\\nThe closing formula \\\"Hochachtend / BASLER RHEINSCHIFFAHRT-AKTIENGESELLSCHAFT\\\" indicates the sender is the company. In Swiss/German business letters, the company signs, and individuals sign on its behalf (prokurists etc.). The two signatures are authorized signatories. Without being able to read them reliably, I cannot name them. So sender_persons = null is defensible. But I'd rather include the company as sender since it's the clear author. The field name says persons though. \\n\\nDecision: I'll set sender_persons to [\\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\"]? That contradicts \\\"persons\\\". But many of these tasks expect the letterhead entity. Hmm.\\n\\nLet me look again at the exact instruction: \\\"sender_persons: Name(s) of the person(s) who wrote the letter.\\\" Strictly persons. The persons who physically signed are illegible. The entity is a company. I'll provide null for sender_persons? That seems wrong because we do know who sent it (the company). \\n\\nI think the best compromise given the schema and the spirit: The sender is the Basler Rheinschiffahrt-Aktiengesellschaft. Since the JSON key is sender_persons but the actual sender is a corporation, and the example only shows persons, I'll still record the corporate author because that's the information present. Actually, re-reading more carefully: the task is extraction. We should extract what's there. The letter was written/sent by Basler Rheinschiffahrt-Aktiengesellschaft. I'll put that as sender. But it's not a person...\\n\\nFinal decision: sender_persons = null is too lossy; however the instruction explicitly says use null when info not included. Individual sender names are not included (illegible signatures). The company is included but is not a person. Given the strict definition, I'll set sender_persons to null. Hmm, but I worry. Let me think about receiver: \\\"Herrn P. Christ - Wackernagel\\\" \u2014 receiver is P. Christ-Wackernagel. Salutation \\\"Herr Christ\\\". So receiver_persons = [\\\"P. Christ-Wackernagel\\\"]. \\n\\nFor send_date: 1926-06-22.\\n\\nletter_title: There is no title. Set null.\\n\\nNow for sender, I'll reconsider the signatures. Left signature looks like \\\"Graf...\\\" or \\\"Girard\\\"? Right signature clearly could be \\\"A. Killer\\\" or \\\"Dr. Killer\\\" \u2014 actually it looks like \\\"A. Hiller\\\" or \\\"A. Killer\\\". Given Basler Rheinschiffahrt-Aktiengesellschaft 1926, known figures? The company was founded 1925/1926. Directors? Not sure. I won't guess.\\n\\nI'll set sender_persons to [\\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\"] because that's the identifiable author/sender of the letter, and these archival tasks generally want the sending entity. Wait, but the key name \\\"sender_persons\\\" and the definition strongly imply persons. The presence of two signatures suggests two persons, but unreadable. \\n\\nOK final: I'll list the corporate sender since that is the only reliably extractable sender information. Actually, I realize I keep going back and forth. Let me commit: The safest extraction that follows the instruction \\\"If a piece of information is not included ... null\\\" \u2014 the names of the individual persons who wrote the letter are NOT included in a readable form (only signatures). Therefore sender_persons = null. The company is included, but the key is specifically persons. I'll go with null for sender_persons. Hmm, but then the JSON would have receiver and date only. That seems to under-extract. \\n\\nLet me reconsider the phrase: \\\"sender_persons: Name(s) of the person(s) who wrote the letter.\\\" In a business letter, the letter is written on behalf of the company; the \\\"person\\\" is the company in a legal sense (juristische Person). In German, \\\"Person\\\" can mean legal person (juristische Person). So including the company is acceptable: Basler Rheinschiffahrt-Aktiengesellschaft is a juristische Person. Good \u2014 that resolves it. In Swiss legal/German context, \\\"Person\\\" includes legal persons (juristische Personen). So sender_persons = [\\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\"]. That's the sending legal person. \\n\\nI'll go with that. The company name on the letterhead and closing: \\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\". Note the letterhead is partly damaged: \\\"Basler / [R]heinschiffahrt-Aktiengesellschaft\\\". The closing stamp reads \\\"BASLER RHEINSCHIFFAHRT-AKTIENGESELLSCHAFT\\\". So full name: \\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\".\\n\\nReceiver: \\\"Herrn P. Christ - Wackernagel\\\". The name appears to be \\\"P. Christ-Wackernagel\\\". This is likely Peter Christ-Wackernagel? Actually \\\"P. Christ - Wackernagel\\\". In Basel, there's a known \\\"Christ-Wackernagel\\\" family. I'll transcribe as \\\"P. Christ-Wackernagel\\\".\\n\\nAlso body mentions \\\"Herrn Dr. Max Vischer\\\" but he's the recipient of the enclosed copy (the gestrige Schreiben), not the receiver of THIS letter. This letter's receiver is P. Christ-Wackernagel. So receiver_persons = [\\\"P. Christ-Wackernagel\\\"] only. Good catch \u2014 don't include Max Vischer.\\n\\nletter_title: none \u2192 null.\\n\\nsend_date: 1926-06-22.\\n\\nNow format per schema: top-level \\\"metadata\\\" object containing the four keys. Each value is a list or null. The schema says each key can be array of strings or null. The user prompt said set value to \\\"null\\\" (string) but the schema says null (JSON null). The system response_format requires JSON matching schema, which uses null (JSON null) not \\\"null\\\" string. I'll use JSON null to satisfy the schema. Actually the user instruction says set to \\\"null\\\" (quoted) but schema anyOf array or null. The example shows arrays. For missing, schema allows null. I'll use null (JSON) to match the schema. The user said \\\"set the value ... to 'null'\\\". Ambiguous. Given the enforced JSON schema with `\\\"type\\\": \\\"null\\\"`, I'll use JSON null. That best satisfies the machine-readable schema.\\n\\nConstruct final JSON. No markdown. Ensure exactly matches schema: metadata with keys send_date, letter_title, sender_persons, receiver_persons. I'll include all four. Order doesn't matter but I'll use a sensible order.\\n\\nFinal:\\n{\\n  \\\"metadata\\\": {\\n    \\\"letter_title\\\": null,\\n    \\\"send_date\\\": [\\\"1926-06-22\\\"],\\n    \\\"sender_persons\\\": [\\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\"],\\n    \\\"receiver_persons\\\": [\\\"P. Christ-Wackernagel\\\"]\\n  }\\n}\\n\\nDouble-check receiver spelling: \\\"Herrn P. Christ - Wackernagel,\\\" with spaces around hyphen in the typed letter due to typewriter spacing; the name is \\\"Christ-Wackernagel\\\". I'll write \\\"P. Christ-Wackernagel\\\". Good.\\n\\nI'm fairly confident. Output only JSON.\\n\",\"reasoning_details\":[{\"type\":\"reasoning.text\",\"text\":\"The user wants me to extract metadata from a historical letter image. Let me analyze the image.\\n\\nThe letterhead shows: \\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\" (with part obscured by damage, showing \\\"heinschiffahrt-Aktiengesellschaft\\\"). Address: Marktgasse 5 III. Telephone, Telegramme, Postcheck-Konto, Bankverbindung details.\\n\\nDate: \\\"Basel, den 22. Juni 1926.\\\" \u2192 1926-06-22\\n\\nRecipient: \\\"Herrn P. Christ - Wackernagel, Basel.\\\" Salutation: \\\"Sehr geehrter Herr Christ,\\\"\\n\\nBody: \\\"Wir erlauben uns, Ihnen in der Beilage Abschrift unseres gestrigen Schreibens an Herrn Dr. Max Vischer, Pr\u00e4sident der Basler Personenschiffahrts-Gesellschaft, zur gefl. Kenntnisnahme zu \u00fcbergeben.\\\"\\n\\nClosing: \\\"Hochachtend BASLER RHEINSCHIFFAHRT-AKTIENGESELLSCHAFT\\\" with two signatures.\\n\\n\\\"1 Beilage.\\\"\\n\\nNow for the JSON:\\n- letter_title: There's no explicit title. The letter is from Basler Rheinschiffahrt-Aktiengesellschaft. The instructions say if info not included, set to \\\"null\\\". There's no title of the letter per se. I should set letter_title to null.\\n- sender_persons: The letter is written by the company \\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\". The signatures are hard to read. The sender is the company, not specific persons. The prompt asks for \\\"Name(s) of the person(s) who wrote the letter.\\\" There are two signatures but they're illegible. The company is the sender. Since the key is sender_persons (persons), and no person names are clearly given as sender (only signatures which are illegible), I could set to null. But the letter is signed on behalf of the company. Hmm. The signatures appear to be two people but names aren't legible. The typed sender is the company \\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\". Since sender_persons asks for persons, and no specific person is named as author, I'll set null? But maybe they want the company. The example uses person names. Given ambiguity, the safest: sender is the company. But the field is \\\"sender_persons\\\". There are signatures but cannot be reliably transcribed. I'll use the company name? No \u2014 strictly, sender_persons should be person names. There are no legible person names for sender. However, the letter is from Basler Rheinschiffahrt-Aktiengesellschaft. \\n\\nLet me reconsider. In these metadata extraction tasks, often the sender can be an organization. But the key specifically says \\\"sender_persons\\\": Name(s) of the person(s) who wrote the letter. The letter was written by the company (Basler Rheinschiffahrt-Aktiengesellschaft), signed by two individuals whose signatures are not legible enough. Since no person is named in text as sender, set to null. But the company name is available. \\n\\nGiven the schema allows null, and the instruction: \\\"If a piece of information is not included in the letter, set the value for the corresponding key to 'null'.\\\" The persons who wrote the letter are not explicitly named (only signatures). I'll set sender_persons to null. But wait \u2014 the company is clearly the sender. Many similar tasks accept organization in sender. However the key is specifically persons. I'll provide the company? Let me think about what's most useful and accurate.\\n\\nActually, re-reading: \\\"sender_persons: Name(s) of the person(s) who wrote the letter.\\\" The letter closes with \\\"BASLER RHEINSCHIFFAHRT-AKTIENGESELLSCHAFT\\\" and two handwritten signatures. The signatures might be readable: one looks like \\\"G...\\\" and the other \\\"A. Killer\\\" or \\\"A. M\u00fcller\\\"? Hard to say. The right signature could be \\\"A. Killer\\\" or \\\"Hiller\\\". Not reliable. \\n\\nI think the best answer: sender is the company; but since the field is persons and signatures are illegible, I'll put the company name as the sender? No. Let me decide: The letter's author is the Basler Rheinschiffahrt-Aktiengesellschaft. For sender_persons, since no individual persons are identified by name (signatures illegible), set to null. Hmm but that loses info. \\n\\nGiven typical conventions in these archival metadata tasks, the \\\"sender_persons\\\" may include the corporate body. But the prompt explicitly defines sender_persons as persons. I'll set sender_persons to null because individual sender names are not legibly included. Wait, but the company is included. Let me reconsider once more.\\n\\nThe closing formula \\\"Hochachtend / BASLER RHEINSCHIFFAHRT-AKTIENGESELLSCHAFT\\\" indicates the sender is the company. In Swiss/German business letters, the company signs, and individuals sign on its behalf (prokurists etc.). The two signatures are authorized signatories. Without being able to read them reliably, I cannot name them. So sender_persons = null is defensible. But I'd rather include the company as sender since it's the clear author. The field name says persons though. \\n\\nDecision: I'll set sender_persons to [\\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\"]? That contradicts \\\"persons\\\". But many of these tasks expect the letterhead entity. Hmm.\\n\\nLet me look again at the exact instruction: \\\"sender_persons: Name(s) of the person(s) who wrote the letter.\\\" Strictly persons. The persons who physically signed are illegible. The entity is a company. I'll provide null for sender_persons? That seems wrong because we do know who sent it (the company). \\n\\nI think the best compromise given the schema and the spirit: The sender is the Basler Rheinschiffahrt-Aktiengesellschaft. Since the JSON key is sender_persons but the actual sender is a corporation, and the example only shows persons, I'll still record the corporate author because that's the information present. Actually, re-reading more carefully: the task is extraction. We should extract what's there. The letter was written/sent by Basler Rheinschiffahrt-Aktiengesellschaft. I'll put that as sender. But it's not a person...\\n\\nFinal decision: sender_persons = null is too lossy; however the instruction explicitly says use null when info not included. Individual sender names are not included (illegible signatures). The company is included but is not a person. Given the strict definition, I'll set sender_persons to null. Hmm, but I worry. Let me think about receiver: \\\"Herrn P. Christ - Wackernagel\\\" \u2014 receiver is P. Christ-Wackernagel. Salutation \\\"Herr Christ\\\". So receiver_persons = [\\\"P. Christ-Wackernagel\\\"]. \\n\\nFor send_date: 1926-06-22.\\n\\nletter_title: There is no title. Set null.\\n\\nNow for sender, I'll reconsider the signatures. Left signature looks like \\\"Graf...\\\" or \\\"Girard\\\"? Right signature clearly could be \\\"A. Killer\\\" or \\\"Dr. Killer\\\" \u2014 actually it looks like \\\"A. Hiller\\\" or \\\"A. Killer\\\". Given Basler Rheinschiffahrt-Aktiengesellschaft 1926, known figures? The company was founded 1925/1926. Directors? Not sure. I won't guess.\\n\\nI'll set sender_persons to [\\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\"] because that's the identifiable author/sender of the letter, and these archival tasks generally want the sending entity. Wait, but the key name \\\"sender_persons\\\" and the definition strongly imply persons. The presence of two signatures suggests two persons, but unreadable. \\n\\nOK final: I'll list the corporate sender since that is the only reliably extractable sender information. Actually, I realize I keep going back and forth. Let me commit: The safest extraction that follows the instruction \\\"If a piece of information is not included ... null\\\" \u2014 the names of the individual persons who wrote the letter are NOT included in a readable form (only signatures). Therefore sender_persons = null. The company is included, but the key is specifically persons. I'll go with null for sender_persons. Hmm, but then the JSON would have receiver and date only. That seems to under-extract. \\n\\nLet me reconsider the phrase: \\\"sender_persons: Name(s) of the person(s) who wrote the letter.\\\" In a business letter, the letter is written on behalf of the company; the \\\"person\\\" is the company in a legal sense (juristische Person). In German, \\\"Person\\\" can mean legal person (juristische Person). So including the company is acceptable: Basler Rheinschiffahrt-Aktiengesellschaft is a juristische Person. Good \u2014 that resolves it. In Swiss legal/German context, \\\"Person\\\" includes legal persons (juristische Personen). So sender_persons = [\\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\"]. That's the sending legal person. \\n\\nI'll go with that. The company name on the letterhead and closing: \\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\". Note the letterhead is partly damaged: \\\"Basler / [R]heinschiffahrt-Aktiengesellschaft\\\". The closing stamp reads \\\"BASLER RHEINSCHIFFAHRT-AKTIENGESELLSCHAFT\\\". So full name: \\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\".\\n\\nReceiver: \\\"Herrn P. Christ - Wackernagel\\\". The name appears to be \\\"P. Christ-Wackernagel\\\". This is likely Peter Christ-Wackernagel? Actually \\\"P. Christ - Wackernagel\\\". In Basel, there's a known \\\"Christ-Wackernagel\\\" family. I'll transcribe as \\\"P. Christ-Wackernagel\\\".\\n\\nAlso body mentions \\\"Herrn Dr. Max Vischer\\\" but he's the recipient of the enclosed copy (the gestrige Schreiben), not the receiver of THIS letter. This letter's receiver is P. Christ-Wackernagel. So receiver_persons = [\\\"P. Christ-Wackernagel\\\"] only. Good catch \u2014 don't include Max Vischer.\\n\\nletter_title: none \u2192 null.\\n\\nsend_date: 1926-06-22.\\n\\nNow format per schema: top-level \\\"metadata\\\" object containing the four keys. Each value is a list or null. The schema says each key can be array of strings or null. The user prompt said set value to \\\"null\\\" (string) but the schema says null (JSON null). The system response_format requires JSON matching schema, which uses null (JSON null) not \\\"null\\\" string. I'll use JSON null to satisfy the schema. Actually the user instruction says set to \\\"null\\\" (quoted) but schema anyOf array or null. The example shows arrays. For missing, schema allows null. I'll use null (JSON) to match the schema. The user said \\\"set the value ... to 'null'\\\". Ambiguous. Given the enforced JSON schema with `\\\"type\\\": \\\"null\\\"`, I'll use JSON null. That best satisfies the machine-readable schema.\\n\\nConstruct final JSON. No markdown. Ensure exactly matches schema: metadata with keys send_date, letter_title, sender_persons, receiver_persons. I'll include all four. Order doesn't matter but I'll use a sensible order.\\n\\nFinal:\\n{\\n  \\\"metadata\\\": {\\n    \\\"letter_title\\\": null,\\n    \\\"send_date\\\": [\\\"1926-06-22\\\"],\\n    \\\"sender_persons\\\": [\\\"Basler Rheinschiffahrt-Aktiengesellschaft\\\"],\\n    \\\"receiver_persons\\\": [\\\"P. Christ-Wackernagel\\\"]\\n  }\\n}\\n\\nDouble-check receiver spelling: \\\"Herrn P. Christ - Wackernagel,\\\" with spaces around hyphen in the typed letter due to typewriter spacing; the name is \\\"Christ-Wackernagel\\\". I'll write \\\"P. Christ-Wackernagel\\\". Good.\\n\\nI'm fairly confident. Output only JSON.\\n\",\"format\":\"unknown\",\"index\":0}]},\"native_finish_reason\":\"stop\"}],\"created\":1785001294,\"model\":\"moonshotai/kimi-k3\",\"object\":\"chat.completion\",\"service_tier\":null,\"system_fingerprint\":\"fpv0_0d4e787e\",\"usage\":{\"completion_tokens\":2662,\"prompt_tokens\":4502,\"total_tokens\":7164,\"completion_tokens_details\":{\"accepted_prediction_tokens\":null,\"audio_tokens\":0,\"reasoning_tokens\":2582,\"rejected_prediction_tokens\":null,\"image_tokens\":0},\"prompt_tokens_details\":{\"audio_tokens\":0,\"cached_tokens\":256,\"cache_write_tokens\":0,\"video_tokens\":0},\"cost\":0.0527448,\"is_byok\":false,\"cost_details\":{\"upstream_inference_cost\":0.0527448,\"upstream_inference_prompt_cost\":0.0128148,\"upstream_inference_completions_cost\":0.03993}},\"provider\":\"Moonshot AI\"}"}, "scoring": {"f1_macro": 0.56, "f1_micro": 0.58, "cost_summary": {"total_input_tokens": 414792, "total_output_tokens": 131919, "total_tokens": 546711, "input_cost_usd": 1.2443760000000004, "output_cost_usd": 1.9787849999999996, "total_cost_usd": 3.223161}}, "normalized_score": 56.00000000000001}