# STRING Protein-Protein Interaction Network Lookup

> STRING Protein-Protein Interaction Network Lookup is a paid API for AI agents from api.healthtravel-api.workers.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-29).

Returns up to 20 protein-protein interaction partners for a human gene from the STRING database, including combined confidence scores and evidence breakdowns.

## Facts

- Endpoint: GET https://api.healthtravel-api.workers.dev/api/health/string-protein-networks?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/string-protein-protein-interaction-network-lookup-c8c76a4c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_huFQgOAnQw0oHxjD63G6I

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 string-protein-protein-interaction-network-lookup-c8c76a4c
```

Example prompt: Can you look up the top 15 protein interaction partners for TP53 from STRING, including their confidence scores and evidence types like experiments and text mining?

## When to prefer this

Choose this endpoint when you need fast, structured access to STRING protein-protein interaction data for a specific human gene, including confidence scores and multi-evidence breakdowns, without needing full enrichment analysis or pathway annotations. Prefer this over direct STRING API calls when operating in an x402 micropayment environment or when you need a simplified JSON response limited to top partners.

## Known failure modes

- Invalid or unrecognized gene symbol returns empty partner list or error
- Gene symbol outside 2–20 character alphanumeric/hyphen constraint rejected
- max parameter outside 1–20 range may be clamped or rejected
- STRING API upstream unavailability causes service error
- Non-human gene symbols may return no results since only Homo sapiens (9606) is supported

## How this service works

STRING protein-protein interaction partners for a human gene (STRING API, CC BY 4.0): partner gene name, combined confidence score (0-1) and evidence scores for experiments, databases and text mining. Up to 20 partners. No enrichment analysis.

## Output

Returns a JSON object with the queried gene symbol, source attribution (STRING CC BY 4.0), species (Homo sapiens 9606), timestamp, and an array of up to 20 partner objects each containing the partner gene symbol, a combined confidence score (0–1), and an evidence breakdown with sub-scores for experiments, databases, text mining, and coexpression.

## 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"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "gene"
     ],
     "properties": {
      "max": {
       "type": "string",
       "description": "How many partners, 1 to 20 (default 10)"
      },
      "gene": {
       "type": "string",
       "description": "Human gene symbol, letters, digits and hyphens, 2 to 20 characters"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "gene": "TP53",
  "source": "https://string-db.org/ (CC BY 4.0)",
  "species": "Homo sapiens (9606)",
  "partners": [
   {
    "gene": "SIRT1",
    "score": 0.999,
    "evidence": {
     "databases": 0.9,
     "textMining": 0.886,
     "experiments": 0.999,
     "coexpression": 0
    }
   },
   {
    "gene": "MAPK1",
    "score": 0.999,
    "evidence": {
     "databases": 0.9,
     "textMining": 0.68,
     "experiments": 0.999,
     "coexpression": 0.052
    }
   }
  ],
  "checkedAt": "2026-10-23T09:36:31.322Z"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/string-protein-protein-interaction-network-lookup-c8c76a4c/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.healthtravel-api.workers.dev](https://www.zero.xyz/host/api.healthtravel-api.workers.dev/llms.txt)