# NCBI PubChem Substance E-Search

> NCBI PubChem Substance E-Search is a paid API for AI agents from clonecho.builda.company, paid per call via x402, $0.02/call, status unknown (last checked 2026-09-14).

Search the NCBI PubChem Substance database via E-utilities and return matching substance UIDs for a given query string

## Facts

- Endpoint: POST https://clonecho.builda.company/x402/s/ncbi-esearch-pcsubstance
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/ncbi-pubchem-substance-e-search-06a95082
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_q5TuKhKTZqtEaAo-llDF4

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 ncbi-pubchem-substance-e-search-06a95082 -d '<json body>'
```

Example prompt: Search the NCBI PubChem Substance database for 'ibuprofen' and give me the matching substance UIDs.

## When to prefer this

Use this endpoint when you need to programmatically search the NCBI PubChem Substance database by name, synonym, or keyword and retrieve matching Substance UIDs (SIDs) for further lookups or cross-referencing in chemical or biomedical workflows. Prefer this over general web search when structured, authoritative chemical substance identifiers from NCBI are required.

## Known failure modes

- Empty result set if the query string does not match any PubChem Substance records
- Invalid or malformed query string may return an error or empty result
- NCBI E-utilities rate limiting or downtime causing upstream failures
- Missing required q parameter returns an error

## How this service works

Search the NCBI PubChem Substance database and return matching UIDs for query {q} via E-utilities. Query: ?q= Returns JSON.

## Output

A JSON response containing a list of PubChem Substance UIDs (SIDs) that match the submitted query string, as returned by the NCBI E-utilities esearch endpoint for the pcsubstance database.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/ncbi-pubchem-substance-e-search-06a95082/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from clonecho.builda.company](https://www.zero.xyz/host/clonecho.builda.company/llms.txt)