# MIME Toolkit – Extension Lookup

> MIME Toolkit – Extension Lookup is a paid API for AI agents from mime.openverbs.com, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).

Returns the file extension(s) associated with a given MIME type string

## Facts

- Endpoint: POST https://mime.openverbs.com/v1/extension
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/mime-toolkit-extension-lookup-db6bce28
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_3Hp4TXb-FsaZutExxP_11

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability mime-toolkit-extension-lookup-db6bce28 -d '<json body>'
```

Example prompt: What file extension goes with the MIME type 'application/vnd.openxmlformats-officedocument.wordprocessingml.document'?

## When to prefer this

Choose this endpoint when you need a quick, authoritative lookup of file extensions from MIME type strings — particularly useful in file handling pipelines, download managers, or upload validators where you have a content-type header and need to derive the correct file extension without maintaining your own MIME database.

## Known failure modes

- Unknown or non-standard MIME type returns empty or null extension list
- Malformed MIME type string (e.g. missing slash) may return an error or empty result
- MIME types with no registered extension (e.g. vendor-specific types) may not resolve
- Rate limiting or payment failure if x402 payment header is missing or invalid

## How this service works

Resolve a MIME type to its default file extension.

## Output

The endpoint returns the standard file extension or extensions associated with the provided MIME type, enabling correct file naming, storage, or routing based on content type information.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "required": [
      "mimeType"
     ],
     "properties": {
      "mimeType": {
       "type": "string",
       "maxLength": 256,
       "minLength": 1,
       "description": "A MIME type, e.g. \"text/html\"."
      }
     },
     "additionalProperties": false
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/mime-toolkit-extension-lookup-db6bce28/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from mime.openverbs.com](https://www.zero.xyz/host/mime.openverbs.com/llms.txt)