# lilambd Constants Lookup by ID

> lilambd Constants Lookup by ID is a paid API for AI agents from api.lilambd.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-11-02).

Retrieves a named physical or mathematical constant by its identifier from the lilambd constants database

## Facts

- Endpoint: GET https://api.lilambd.com/units/constants/%7Bid%7D?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-11-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/lilambd-constants-lookup-by-id-f6e8ef0f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_1ehWcUTi5_aLJOrhGSJP_

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 lilambd-constants-lookup-by-id-f6e8ef0f
```

Example prompt: Can you look up the physical constant with ID 'planck' from the lilambd constants database and give me its value and attribution?

## When to prefer this

Use this endpoint when you need to programmatically retrieve a specific physical, mathematical, or scientific constant by a known identifier and require source attribution alongside the value. Prefer this over manual lookup when building scientific computation pipelines, citation tools, or educational apps that need verified constant values with licence information.

## Known failure modes

- Unknown or invalid constant ID returns empty data array with count 0
- Malformed path parameter may result in a 404 or error response
- Payment failure (x402) prevents access to the endpoint
- No schema-level validation on query params may cause silent ignoring of extras

## How this service works

A crossing for play, feeling, language, science and computation — creating states that do not have names yet.

## Output

Returns a JSON object with a 'data' array containing the constant's details, a 'count' of results returned, and an 'attribution' string with the source licence line for the constant data.

## 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",
    "queryParams",
    "pathParams"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "pathParams": {
     "type": "object",
     "required": [
      "id"
     ],
     "properties": {
      "id": {
       "type": "string"
      }
     }
    },
    "queryParams": {
     "type": "object",
     "required": [],
     "properties": {},
     "additionalProperties": {
      "type": "string"
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "json"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "data": [],
  "count": 0,
  "attribution": "source licence line"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/lilambd-constants-lookup-by-id-f6e8ef0f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.lilambd.com](https://www.zero.xyz/host/api.lilambd.com/llms.txt)