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4byte Function Signature by Selector

fourbyte/function-by-selector

Looks up the text signatures that 4byte.directory has recorded for a 4-byte function selector (the first four bytes of EVM calldata, for example 0xa9059cbb). Returns every candidate: the database is crowd-sourced, so collisions and junk entries appear next to the real one (the oldest entry is usually the genuine one). This is 4byte.directory, a different source from the OpenChain/Sourcify signature database; the two can disagree.

activeper callv1

Price

$0.0026 per call

You pay the price shown. If a call turns out to cost more than its quote, you pay the actual price, capped at twice the quote. No monthly minimum. Top-ups start at $0.50.

Data source

4byte.directory

Function and event signatures from the public 4byte.directory API (https://www.4byte.directory). Served by Eden Engine; not an official 4byte.directory product.

Use it

Five steps: search, inspect, learn, run, settle. No per-tool setup; your agent reaches this tool through the meta-tools it already has.

Connect once and your AI can find and run this tool, and any other it needs.

Install itCreate an account
agent
// 1. search: find the tool
omnial_search({ query: "what you need" })

// 2. inspect: price and input schema
omnial_inspect({ tool: "fourbyte/function-by-selector" })

// 3. learn: read the usage guide at runtime
omnial_learn({ tool: "fourbyte/function-by-selector" })

// 4. run: price the exact call first, then run it
omnial_execute({ tool: "fourbyte/function-by-selector", input: { /* see input_schema */ }, dry_run: true })
omnial_execute({ tool: "fourbyte/function-by-selector", input: { /* ... */ } })

// 5. settle: the call is charged when it finishes, nothing to do

Not connected yet? Point your MCP client at https://mcp.eden-engine.com/mcp, then copy a config for your client.

Pricing

Every charge this tool can incur.

ChargePrice
Per call
$0.0026
Updated
Oct 21, 2026

Input and output schemas

Input schema
input_schema.json
{
  "type": "object",
  "required": [
    "hex_signature"
  ],
  "properties": {
    "hex_signature": {
      "type": "string",
      "pattern": "^0x[0-9a-fA-F]{8}$",
      "description": "Function selector: 0x followed by 8 hex digits."
    }
  },
  "additionalProperties": false
}
Output schema
output_schema.json
{
  "type": "object",
  "required": [
    "count",
    "next",
    "previous",
    "results"
  ],
  "properties": {
    "next": {
      "type": "null"
    },
    "count": {
      "type": "number"
    },
    "results": {
      "type": "array",
      "items": {}
    },
    "previous": {
      "type": "null"
    }
  },
  "description": "Wrapper with a count, paging links and the first page of matches.",
  "additionalProperties": true
}