Previous value: -"The user's own sender details: their REAL full name (first and last name, not an alias, nickname or pseudonym) and postal address, any country. Optional: needed only while the account has no sender details yet; they are then checked and saved to the account, kept on record and never printed on the envelope or in the letter. Once the account has them, the saved details are used and this is not saved (the user changes them in Settings → Your details)."New value: +"The user's own sender details: their REAL full name (first and last name, not an alias, nickname or pseudonym) and postal address, any country. Optional: needed only while the account has no sender details yet; they are then checked and saved to the account. Once the account has them, the saved details are used and this is not saved (the user changes them in Settings → Your details)."

Added value: +{
+  "description": "The user's own sender details: their REAL full name (first and last name, not an alias, nickname or pseudonym) and postal address, any country. Optional: needed only while the account has no sender details yet; they are then checked and saved to the account, kept on record and never printed on the envelope or in the letter. Once the account has them, the saved details are used and this is not saved (the user changes them in Settings → Your details).",
+  "properties": {
+    "city": {
+      "description": "City or town, e.g. Berlin.",
+      "maxLength": 50,
+      "minLength": 1,
+      "type": "string"
+    },
+    "company": {
+      "description": "The user's company or organisation, e.g. Example GmbH. Optional.",
+      "maxLength": 60,
+      "type": "string"
+    },
+    "country": {
+      "description": "Country as an ISO 3166-1 alpha-2 code, e.g. DE, FR or US.",
+      "maxLength": 2,
+      "minLength": 2,
+      "type": "string"
+    },
+    "line1": {
+      "description": "Street and house number, or PO box, e.g. Hauptstraße 5.",
+      "maxLength": 60,
+      "minLength": 1,
+      "type": "string"
+    },
+    "line2": {
+      "description": "Optional extra address line: c/o, apartment, floor or building, e.g. Apt 4B.",
+      "maxLength": 60,
+      "type": "string"
+    },
+    "name": {
+      "description": "The user's full name: their REAL first and last name, not an alias, nickname or pseudonym, e.g. Anna Schmidt.",
+      "maxLength": 60,
+      "minLength": 1,
+      "type": "string"
+    },
+    "postal_code": {
+      "description": "Postcode / ZIP code, e.g. 10115 or 94105. Required in countries that use postcodes.",
+      "maxLength": 16,
+      "type": "string"
+    },
+    "region": {
+      "description": "State, province or region where the user's country has one in addresses, e.g. CA (California, US), ON (Ontario, CA) or Madrid (ES). Required for addresses in AE, AS, AU, BR, CA, CN, CO, CR, ES, FM, HK, HN, ID, IN, IQ, IT, JM, JP, KN, KR, KY, MH, MP, MX, NR, PF, PG, PW, RU, SO, SV, TW, US, VE, VI, VN when this block is saved as the user's sender details (an account without them yet: SENDER_DETAILS_REQUIRED, fields.region); otherwise optional.",
+      "maxLength": 50,
+      "type": "string"
+    }
+  },
+  "required": [
+    "name",
+    "line1",
+    "city",
+    "country"
+  ],
+  "type": "object"
+}

Added value: +"\"bw\" = black and white, \"color\" = colour printing (costs more per page). Default \"bw\"."

Added value: +"The PDF to post: document_id from upload_document or compose_letter, e.g. doc_2h7k9m4q8x1v3c6b0n5p. Pass document_id or upload_id."

Added value: +"true = print on both sides of the paper (fewer sheets, so a lighter letter); false = one side only. Default false."

Added value: +"\"DL\" (220×110 mm, letter folded twice), \"C5\" (229×162 mm, folded once) or \"C4\" (324×229 mm, flat). Omit to use the smallest envelope that holds the sheets (recommended); one too small for the page count is refused."

Previous value: -"Only for a US Letter PDF to a recipient outside US, CA, PR, VI, GU, AS, MP (the US, Canada and US territories): \"a4\" = shrink to A4 (recommended), \"us_letter\" = keep US Letter. Ask the user; same price. Ignored otherwise (A4 PDFs print on A4, US Letter PDFs to those countries on US Letter)."New value: +"Only for a US Letter PDF to a recipient outside US, CA, PR, VI, GU, AS, MP (the US, Canada and US territories): \"a4\" = shrink to A4 (recommended), \"us_letter\" = keep US Letter. Ask the user; same price. Ignored otherwise (A4 PDFs print on A4, US Letter PDFs to those countries on US Letter). No default: omit until the user has chosen."

Added value: +"Recipient's postal address, printed on the envelope. Ask the user for missing fields."

Added value: +"City or town, e.g. Berlin."

Previous value: -"Company or organisation (optional)"New value: +"Recipient's company or organisation, e.g. Example GmbH. Optional."

Previous value: -"ISO 3166-1 alpha-2 country code, e.g. DE, FR, US"New value: +"Country as an ISO 3166-1 alpha-2 code, e.g. DE, FR or US."

Previous value: -"Street and house number, or PO box"New value: +"Street and house number, or PO box, e.g. Hauptstraße 5."

Previous value: -"Additional line: c/o, apartment, building"New value: +"Optional extra address line: c/o, apartment, floor or building, e.g. Apt 4B."

Previous value: -"Recipient (person) name"New value: +"Recipient's name: a person, or a department such as Customer Service when writing to a company, e.g. Erika Mustermann."

Previous value: -"Postcode / ZIP (required in most countries)"New value: +"Postcode / ZIP code, e.g. 10115 or 94105. Required in countries that use postcodes."

Previous value: -"State / province where the country uses it (e.g. US state code CA)"New value: +"State, province or region. Required for recipients in AE, AS, AU, BR, CA, CN, CO, CR, ES, FM, HK, HN, ID, IN, IQ, IT, JM, JP, KN, KR, KY, MH, MP, MX, NR, PF, PG, PW, RU, SO, SV, TW, US, VE, VI, VN (without it the draft is refused: INVALID_ADDRESS, fields.region); omit where addresses have none, e.g. DE, FR or GB. The code in US, CA, AU and BR, e.g. CA (California) or ON (Ontario); elsewhere the name or its usual abbreviation, e.g. Madrid (ES) or RM (Rome, IT)."

Previous value: -"Registered mail (tracking + signature on delivery)"New value: +"true = registered mail: tracking number and signature on delivery, for an extra fee (also what \"certified\" letters, Einschreiben, lettre recommandée and carta certificada mean here; not a US certified-mail product). false = ordinary mail. Default false."

Previous value: -"From create_upload_link, once the user has uploaded"New value: +"upload_id from create_upload_link, once the user has uploaded the PDF on that page. Pass document_id or upload_id."

Added value: +{
+  "description": "Only for a US Letter PDF to a recipient outside US, CA, PR, VI, GU, AS, MP (the US, Canada and US territories): \"a4\" = shrink to A4 (recommended), \"us_letter\" = keep US Letter. Ask the user; same price. Ignored otherwise (A4 PDFs print on A4, US Letter PDFs to those countries on US Letter).",
+  "enum": [
+    "a4",
+    "us_letter"
+  ],
+  "type": "string"
+}