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API-existence Oracle: Symbol Exists
x402
API-existence Oracle: Symbol Exists is a paid API for AI agents from attester.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-16).
Checks whether a named symbol (e.g. function, class, or variable) exists in a given codebase or package registry.
Price / call$0.005
Success—
StatusUnknown
How this service works
Deterministic symbol existence for PyPI and npm packages: functions, classes, methods, constants with signatures and deprecation flags, extracted from real artifacts. Negative answers include closest matches and signed proof. $0.005 USDC per check.
Output
Returns a boolean indicating whether the specified symbol exists, along with any available metadata about the symbol such as its type, export status, or location within the package.
Example use cases
Verify function before code generation
“Before you write any code that calls `useQuery` from the `@tanstack/react-query` package, can you confirm that symbol actually exists and is exported so we don't generate broken imports?”
Check deprecated method still available
“I need to know if `connect` is still defined and accessible in the `mongoose` package — can you verify it exists before I update our database initialization code?”
Validate type exists in SDK
“Can you check whether the `AuthSession` type is actually exported from the `@supabase/auth-helpers-nextjs` package? I want to make sure it's there before I use it in our TypeScript interfaces.”
Technical details
Endpoint
POSThttps://attester.dev/v1/symbol/existsWhen to prefer
Use this endpoint when you need to programmatically verify whether a named symbol (function, class, type, variable) is defined and accessible within a package or codebase, especially before generating code that depends on it or before making API calls that reference it. Prefer this over a full package diff endpoint when you only need a targeted existence check rather than change history.
Side effects
- Symbol name or package not provided — returns validation error
- Unknown or misspelled package name — returns not-found or error response
- Symbol exists but is not exported — may return false or qualified result
- Payment not provided or insufficient — returns 402 Payment Required
- Rate limit exceeded — returns 429 or payment error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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