API reference · CAIN Eval

Grade Trajectory

POST /fabric/eval/trajectory/grade

Last reviewed 2026-11-06

POST /fabric/eval/trajectory/grade

Grade a successful agent trajectory for path quality.

Computes: - Redundant calls (exact tool+args repeats) - Wasted cost (steps not ancestors of terminal) - Risky-then-corrected patterns

Returns 0-1 score where 1 = optimal path.

Request body

TrajectoryGradeRequest (required)

Field	Type	Meaning
`steps` required	array of `TrajectoryStep`
`terminal_step`	integer or null
`trajectory_id`	string or null

Responses

Status	Meaning	Body
`200`	Successful Response	JSON
`401`	The X-API-Key header is missing, or the key is unknown, revoked or replaced.	`Error`
`403`	The key is valid but may not do this (for example an agent key approving its own held action).	`Error`
`422`	Validation Error	`HTTPValidationError`
`429`	Rate limit or monthly quota reached. Wait for the number of seconds in Retry-After when it is sent.	`Error`

Try it

Your API key X-API-Key Remember the key in this tab onlyRequest body application/json

This call changes data in the account the key belongs to.

The request goes from your browser straight to this site. Your key is not stored unless you tick the box, and then only in this tab's session storage.

Code

curl -sS -X POST 'https://cainstudio.online/fabric/eval/trajectory/grade' \
  -H "X-API-Key: $CAIN_API_KEY" \
  -H 'Content-Type: application/json' \
  -d '{"steps": [{"index": 1, "tool": "tool", "cost": 0.0, "risk_tier": "low"}]}'

import json, os, urllib.request

req = urllib.request.Request('https://cainstudio.online/fabric/eval/trajectory/grade', method='POST',
    headers={"X-API-Key": os.environ["CAIN_API_KEY"], "Content-Type": "application/json"},
    data=json.dumps({
      "steps": [
        {
          "index": 1,
          "tool": "tool",
          "cost": 0.0,
          "risk_tier": "low"
        }
      ]
    }).encode())
with urllib.request.urlopen(req, timeout=60) as r:
    print(r.status, json.load(r))

const res = await fetch("https://cainstudio.online/fabric/eval/trajectory/grade", {
  method: "POST",
  headers: {
    "X-API-Key": process.env.CAIN_API_KEY!,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "steps": [
      {
        "index": 1,
        "tool": "tool",
        "cost": 0.0,
        "risk_tier": "low"
      }
    ]
  }),
});
console.log(res.status, await res.json());

Schemas used

Error · HTTPValidationError · TrajectoryGradeRequest · TrajectoryStep · ValidationError

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