x402 service change events

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Matches the readOnlyHint annotation with 'Free and read-only' and adds important caveats beyond the annotation: prices are atomic token amounts not dollars, and payTo values are masked (only change is reported, not the address).

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single run-on sentence with colon-separated lists, making it a bit dense, but it packs all essential details without redundancy. Could be split into clearer sentences.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema exists, so the description compensates by mentioning the return shape (most recent first, event types, full snapshots). It could be more explicit about the exact output fields, but the 'before/after envelope snapshots' hint provides enough context.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

All five parameters have schema descriptions, and the description enriches them: the type enum is explained with concrete meanings, service is tied to the same slug as x402_get_service, and per_page notes that large pages are heavy due to full before/after snapshots.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

Clearly identifies the resource (service change events) and the action (returns a log of payTo, price, and schema changes), with specific triggers for when to call it. Distinguished from siblings by being the change-feed tool rather than search/get/health.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives concrete scenarios: before trusting cached service data and after a payment failure. Does not explicitly name alternatives, but the two use cases make the intended context clear.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.