Paper Plane Post

Postcard Maker

start_postcard

Start a Paper Plane Post postcard: a photo printed on a 4×6 card, with an optional illustrated version of it, mailed first class for $7 with postage included. Mails from the US to 194 countries; the address country is an ISO 3166-1 alpha-2 code. Use photo for an uploaded or ChatGPT-generated image. Other clients can send photo_base64 encoded from the file itself, or photo_url if the image is already online. If no image is available, ask for an uploaded photo or public image URL. Do not call this tool or invent image data. Set is_ai_generated to true for an image you generated or know was AI-generated; its illustration is made only if the person selects Illustrated on the website. Include the note and recipient address if the person has supplied them. If either is missing, start the postcard immediately without asking for it; the person can complete it on the website. Returns a link for the person to open: they see their photo on the card, finish the note and address, can choose the illustrated version, and pay on the website. Nothing is charged or mailed until they do. Never ask for payment details. The link expires after about a week. This tool only starts postcards. It cannot retrieve orders or delivery status; explain that limitation for lookup requests instead of calling it. On a busy day the tool may first answer with a short challenge of four questions to solve and send back in the challenge argument; the proof-of-work question needs a code tool.

Input Schema

Name	Required	Description
`note`	No	The note for the back of the card, if the person told you what to say. Up to 350 characters.
`photo`	No	The uploaded photo or image created in this conversation. Use the actual file supplied by ChatGPT.
`challenge`	No	Only after this tool answered with a challenge: its id, and your answers to its four questions in the order they were asked, each as a short string. Solve the proof-of-work question with a code tool; it needs a few million SHA-256 hashes. Send the rest of the arguments again unchanged.
`photo_url`	No	A public https:// URL of the photo. Use this only when the photo is already online and you don't have the file.
`recipient`	No	Whatever you know of the recipient's mailing address. The person completes and checks it before paying.
`photo_base64`	No	For clients without native file transfer: the photo file's own bytes as base64 or a data: URL, read and encoded with a file or code tool. JPEG, PNG, WebP or HEIC, up to about 10 MB. Never invent base64 from memory or from looking at an image.
`is_ai_generated`	No	Set true when the supplied image was already AI-generated. The website keeps the original and only generates an illustrated version if the person selects Illustrated.

Output Schema

Name	Required	Description	Default
`url`	Yes	The link the person opens to finish and pay for the postcard.

Schema Changelog

Changes observed during successful MCP inspections.

Changed6 schema fields changedNov 7, 2026
- addedInput schema / properties / recipient / properties / city / maxLength
```
Added value: +200
```
- addedInput schema / properties / recipient / properties / line1 / maxLength
```
Added value: +64
```
- addedInput schema / properties / recipient / properties / line2 / maxLength
```
Added value: +64
```
- addedInput schema / properties / recipient / properties / name / maxLength
```
Added value: +40
```
- addedInput schema / properties / recipient / properties / state / maxLength
```
Added value: +200
```
- addedInput schema / properties / recipient / properties / zip / maxLength
```
Added value: +40
```

Changed3 schema fields changedOct 25, 2026

addedInput schema / properties / is_ai_generated

Added value: +{
+  "description": "Set true when the supplied image was already AI-generated. The website keeps the original and only generates an illustrated version if the person selects Illustrated.",
+  "type": "boolean"
+}

addedInput schema / properties / photo

Added value: +{
+  "description": "The uploaded photo or image created in this conversation. Use the actual file supplied by ChatGPT.",
+  "properties": {
+    "download_url": {
+      "format": "uri",
+      "type": "string"
+    },
+    "file_id": {
+      "minLength": 1,
+      "type": "string"
+    },
+    "file_name": {
+      "type": "string"
+    },
+    "mime_type": {
+      "type": "string"
+    }
+  },
+  "required": [
+    "download_url",
+    "file_id"
+  ],
+  "type": "object"
+}

changedInput schema / properties / photo_base64 / description

Previous value: -"Preferred. The photo file's own bytes as base64 or a data: URL: read the file with your file or code tool and encode it. JPEG, PNG, WebP or HEIC, up to about 10 MB. Never write base64 from memory or from looking at an image."New value: +"For clients without native file transfer: the photo file's own bytes as base64 or a data: URL, read and encoded with a file or code tool. JPEG, PNG, WebP or HEIC, up to about 10 MB. Never invent base64 from memory or from looking at an image."

Changed1 schema field changedOct 21, 2026

changedInput schema / properties / recipient / properties / country / enum

Previous value: -[
-  "US",
-  "AL",
-  "DZ",
-  "AD",
-  "AO",
-  "AI",
-  "AG",
-  "AR",
-  "AW",
-  "AU",
-  "AT",
-  "AZ",
-  "BS",
-  "BH",
-  "BD",
-  "BB",
-  "BE",
-  "BZ",
-  "BJ",
-  "BO",
-  "BA",
-  "BW",
-  "BR",
-  "VG",
-  "BN",
-  "BG",
-  "BF",
-  "BI",
-  "KH",
-  "CM",
-  "CA",
-  "CV",
-  "BQ",
-  "KY",
-  "TD",
-  "CL",
-  "CN",
-  "CO",
-  "KM",
-  "CD",
-  "CK",
-  "CR",
-  "HR",
-  "CW",
-  "CY",
-  "CZ",
-  "CI",
-  "DK",
-  "DJ",
-  "DM",
-  "DO",
-  "EC",
-  "EG",
-  "SV",
-  "GQ",
-  "EE",
-  "SZ",
-  "ET",
-  "FK",
-  "FO",
-  "FJ",
-  "FI",
-  "FR",
-  "GA",
-  "GM",
-  "GE",
-  "DE",
-  "GH",
-  "GI",
-  "GR",
-  "GL",
-  "GD",
-  "GT",
-  "GN",
-  "GW",
-  "GY",
-  "HN",
-  "HK",
-  "HU",
-  "IS",
-  "IN",
-  "ID",
-  "IQ",
-  "IE",
-  "IL",
-  "IT",
-  "JM",
-  "JP",
-  "JO",
-  "KZ",
-  "KE",
-  "KW",
-  "KG",
-  "LA",
-  "LV",
-  "LB",
-  "LS",
-  "LR",
-  "LY",
-  "LI",
-  "LT",
-  "LU",
-  "MO",
-  "MG",
-  "MW",
-  "MY",
-  "MV",
-  "ML",
-  "MT",
-  "MR",
-  "MU",
-  "MX",
-  "MD",
-  "MC",
-  "MN",
-  "ME",
-  "MS",
-  "MA",
-  "MZ",
-  "MM",
-  "NA",
-  "NR",
-  "NP",
-  "NL",
-  "NZ",
-  "NI",
-  "NE",
-  "NG",
-  "NU",
-  "NF",
-  "MK",
-  "NO",
-  "OM",
-  "PK",
-  "PA",
-  "PG",
-  "PY",
-  "PE",
-  "PH",
-  "PN",
-  "PL",
-  "PT",
-  "QA",
-  "RO",
-  "RW",
-  "SH",
-  "KN",
-  "LC",
-  "VC",
-  "WS",
-  "SM",
-  "SA",
-  "SN",
-  "RS",
-  "SL",
-  "SG",
-  "SX",
-  "SK",
-  "SI",
-  "SB",
-  "SO",
-  "ZA",
-  "KR",
-  "ES",
-  "LK",
-  "SR",
-  "SE",
-  "CH",
-  "ST",
-  "TW",
-  "TJ",
-  "TZ",
-  "TH",
-  "TL",
-  "TG",
-  "TK",
-  "TO",
-  "TT",
-  "TN",
-  "TC",
-  "TV",
-  "TR",
-  "UG",
-  "UA",
-  "AE",
-  "GB",
-  "UY",
-  "UZ",
-  "VU",
-  "VA",
-  "VE",
-  "VN",
-  "EH",
-  "ZM",
-  "ZW"
-]New value: +[
+  "US",
+  "AL",
+  "DZ",
+  "AD",
+  "AO",
+  "AI",
+  "AG",
+  "AR",
+  "AW",
+  "AU",
+  "AT",
+  "AZ",
+  "BS",
+  "BH",
+  "BD",
+  "BB",
+  "BE",
+  "BZ",
+  "BJ",
+  "BO",
+  "BA",
+  "BW",
+  "BR",
+  "VG",
+  "BN",
+  "BG",
+  "BF",
+  "BI",
+  "KH",
+  "CM",
+  "CA",
+  "CV",
+  "BQ",
+  "KY",
+  "TD",
+  "CL",
+  "CN",
+  "CO",
+  "KM",
+  "CD",
+  "CK",
+  "CR",
+  "HR",
+  "CW",
+  "CY",
+  "CZ",
+  "CI",
+  "DK",
+  "DJ",
+  "DM",
+  "DO",
+  "EC",
+  "EG",
+  "SV",
+  "GQ",
+  "EE",
+  "SZ",
+  "ET",
+  "FK",
+  "FO",
+  "FJ",
+  "FI",
+  "FR",
+  "GA",
+  "GM",
+  "GE",
+  "DE",
+  "GH",
+  "GI",
+  "GR",
+  "GL",
+  "GD",
+  "GT",
+  "GN",
+  "GW",
+  "GY",
+  "HN",
+  "HK",
+  "HU",
+  "IS",
+  "IN",
+  "ID",
+  "IQ",
+  "IE",
+  "IL",
+  "IT",
+  "JM",
+  "JP",
+  "JO",
+  "KZ",
+  "KE",
+  "KW",
+  "KG",
+  "LA",
+  "LV",
+  "LB",
+  "LS",
+  "LR",
+  "LY",
+  "LI",
+  "LT",
+  "LU",
+  "MO",
+  "MG",
+  "MW",
+  "MY",
+  "MV",
+  "ML",
+  "MT",
+  "MR",
+  "MU",
+  "MX",
+  "MD",
+  "MC",
+  "MN",
+  "ME",
+  "MS",
+  "MA",
+  "MZ",
+  "MM",
+  "NA",
+  "NR",
+  "NP",
+  "NL",
+  "NZ",
+  "NI",
+  "NE",
+  "NG",
+  "NU",
+  "NF",
+  "MK",
+  "NO",
+  "OM",
+  "PK",
+  "PA",
+  "PG",
+  "PY",
+  "PE",
+  "PH",
+  "PN",
+  "PL",
+  "PT",
+  "QA",
+  "RO",
+  "RW",
+  "SH",
+  "KN",
+  "LC",
+  "VC",
+  "WS",
+  "SM",
+  "SA",
+  "SN",
+  "RS",
+  "SL",
+  "SG",
+  "SX",
+  "SK",
+  "SI",
+  "SB",
+  "ZA",
+  "KR",
+  "ES",
+  "LK",
+  "SR",
+  "SE",
+  "CH",
+  "ST",
+  "TW",
+  "TJ",
+  "TZ",
+  "TH",
+  "TL",
+  "TG",
+  "TK",
+  "TO",
+  "TT",
+  "TN",
+  "TC",
+  "TV",
+  "TR",
+  "UG",
+  "UA",
+  "AE",
+  "GB",
+  "UY",
+  "UZ",
+  "VU",
+  "VA",
+  "VE",
+  "VN",
+  "EH",
+  "ZM",
+  "ZW"
+]

First observedOct 19, 2026

TDQS

A4.8/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations only declare the safety profile (write, open-world, non-idempotent, non-destructive); the description supplies the behavior that actually shapes a call: $7 with postage, no charge or mailing until the user completes on the website, link expires in about a week, optional illustration only if selected on the site, and a conditional challenge flow requiring a proof-of-work answer plus resubmission of all arguments. Nothing disruptive is hidden.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with what the postcard is and what it costs, then rules, then the challenge edge case — a logical order for an agent to read. It is dense but long, and a few instructions (never invent image data) are repeated in the schema, costing some tightness.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 7-parameter, nested, open-world write tool with an output schema, the description covers the gaps the schema cannot: price, fulfillment timing, link lifetime, what the user sees and does next, and the failure-mode challenge protocol. An agent has enough to decide whether to call and how to recover from a challenge.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3; the description exceeds it by explaining the routing logic between the three image paths (photo vs photo_base64 for clients without file transfer vs photo_url when already online) and the conditional meaning of is_ai_generated. The challenge parameter's retry contract is reinforced in prose, though the country-code format is restated rather than newly clarified.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

Opens with a specific verb and resource ("Start a Paper Plane Post postcard") and immediately defines the artifact: a photo printed on a 4×6 card, optional illustrated version, mailed first class for $7, US to 194 countries. It also explicitly disclaims the sibling's territory ("This tool only starts postcards. It cannot retrieve orders or delivery status"), so an agent can separate it from show_postcard without opening a schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives explicit use and non-use conditions: use photo for uploads/ChatGPT images, photo_url only when the image is already online, "Do not call this tool or invent image data" when no image exists, and do not call it for order lookups. It also resolves the counterintuitive case — if note or recipient is missing, start anyway without asking — and forbids requesting payment details.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All Paper Plane Post tools Inspect

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