# TrialScope — Clinical Trial Change-Delta Lookup

> TrialScope — Clinical Trial Change-Delta Lookup is a paid API for AI agents from x402-trialscope.onrender.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-16).

Retrieves the field-level changes between a stored snapshot and the current ClinicalTrials.gov record for a specific trial, revealing what has changed since the snapshot was taken.

## Facts

- Endpoint: GET https://x402-trialscope.onrender.com/delta?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/trialscope-clinical-trial-change-delta-lookup-182206b1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_PdOKoPDATDu-BVi8Pao7Y

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 trialscope-clinical-trial-change-delta-lookup-182206b1
```

Example prompt: Show me what changed in clinical trial NCT04280705 since snapshot 'snap_abc123' — I want to see every field that was updated.

## When to prefer this

Choose this endpoint when you have a previously created snapshot (via POST /snapshot) and need to see exactly what changed in a specific trial record since that snapshot was taken. It is purpose-built for change-detection workflows on ClinicalTrials.gov data, unlike a fresh search or full dossier fetch. Use it when you need a diff, not a full record pull.

## Known failure modes

- HTTP 402 returned if payment not provided via x402 protocol — caller must pay $0.02 USDC per call
- Invalid or expired snapshotId returns an error indicating the snapshot was not found
- Invalid nctId format returns a validation error
- NCT ID not present in the snapshot returns a mismatch error
- Network or upstream ClinicalTrials.gov API unavailability may cause 503 responses

## How this service works

Per-call clinical trial search, study dossiers, and change-deltas from ClinicalTrials.gov. Paid per call via the x402 protocol (USDC); unpaid requests return HTTP 402 with payment terms in the PAYMENT-REQUIRED header. Terms of service: GET /terms (free).

## Output

Returns a structured diff object showing field-level changes between the stored snapshot and the current ClinicalTrials.gov record for the specified NCT ID, including which fields were added, removed, or modified and their old vs. new values.

## 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": [
      "snapshotId",
      "nctId"
     ],
     "properties": {
      "nctId": {
       "type": "string",
       "description": "NCT id that was in the snapshot"
      },
      "snapshotId": {
       "type": "string",
       "description": "Snapshot id from POST /snapshot"
      }
     }
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/trialscope-clinical-trial-change-delta-lookup-182206b1/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-trialscope.onrender.com](https://www.zero.xyz/host/x402-trialscope.onrender.com/llms.txt)