---
title: "What's happened in a given topic since a given date?"
method: POST
path: "/api/agent/knowledge-delta"
tags: ["agent"]
---

# What's happened in a given topic since a given date?

`POST /api/agent/knowledge-delta`

## Request

- Base URL: `https://2s.io`
- URL: `https://2s.io/api/agent/knowledge-delta`
- Auth: API key in header `PAYMENT-SIGNATURE`

What's happened in a given topic since a given date? Pass a free-text topic + ISO date; receive a deduplicated, ranked list of recent events drawn from US federal regulations, US House + Senate roll-call votes, academic papers (arXiv + PubMed + Semantic Scholar), and federal court opinions. Each event includes title, 1-2 sentence summary, date, source label, source URL, and a 1-5 significance score. Designed so an AI agent can spend one call to catch up on a domain since its LLM training cutoff. LLM-backed source routing and synthesis. Billing: payment settles before this endpoint runs (paid upstream), so an error after settlement IS charged — the error response then carries the payment receipt (PAYMENT-RESPONSE) and `X-2s-Charged: true`.

## Query parameters

- `trial` 1

## Request body

- object
  - `topic` string, required: Free-text domain. Examples: "oncology immunotherapy", "Rust language ecosystem", "SEC enforcement against crypto exchanges".
  - `since` string, required: Earliest date (YYYY-MM-DD). Typically the agent's LLM training cutoff date.
  - `until` string: Latest date (YYYY-MM-DD). Default = today.
  - `maxEvents` integer: Max events to return (1-50). Default 20.

## Other responses

- `200` (unresolved $ref)
- `400`: Invalid request. Parameter validation (BAD_REQUEST / INVALID_PARAM with error.details.issues, MALFORMED_JSON) runs before payment and is never charged; a request-specific 400 raised by the endpoint itself runs after settlement on this paid-upstream operation and IS charged (`X-2s-Charged: true` + PAYMENT-RESPONSE receipt).
- `402`: Payment required. Body is the x402 PaymentRequirements envelope with a multi-network accepts array; the per-call price is in accepts[].amount (and on the operation as x-2s-price). Sign for whichever rail you hold USDC on (EIP-3009 for Base, partial SPL transfer for Solana) and retry with the PAYMENT-SIGNATURE header (X-PAYMENT also accepted for v1 clients). Also PAYMENT_SETTLE_FAILED (error envelope) when a verified payment failed to settle: error.details.chargeStatus is "not_charged" (retry with a fresh payment) or "unknown" (the authorization may still settle before its deadline — check it before retrying).
- `429`: Too many requests — RATE_LIMITED: our per-IP / per-payer limiter. Not charged; retry after Retry-After.
- `5XX`: Server-side failure. 500 INTERNAL: unexpected error; quote error.errorId (also the X-2s-Error-Id header). 502 UPSTREAM_UNAVAILABLE (or another UPSTREAM_* code): the data provider failed — composite endpoints refuse unbilled when every source fails. 503 SERVICE_PAUSED: endpoint paused by the operator kill switch, retry after Retry-After; 503 SPEND_CAP: daily upstream budget exhausted. 504 UPSTREAM_TIMEOUT. On a paid-upstream operation (see its description) this can follow settlement: then the call WAS charged and the response carries `X-2s-Charged: true` plus the PAYMENT-RESPONSE receipt. SERVICE_PAUSED and SPEND_CAP are never charged.

---

[API](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api.md) · [All operations](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api/llms.txt) · [OpenAPI document](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api/revisions/da4c5caf686e?raw)