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

Annotations already declare readOnly, idempotent, and non-destructive hints, and the description adds material non-obvious behavior: events before the observatory archive started cannot be returned, the response reports coverage fields and whether the window predates the archive, and the call costs $0.005 USDC via x402 on Base. This is genuinely useful context beyond the structured annotations.

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 three sentences with each carrying distinct information: what the feed contains, when to use it, and critical operational caveats (archive boundary, response coverage fields, cost). It is front-loaded with the most decision-relevant facts and contains no filler.

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?

For a single-optional-parameter tool with no output schema, the description covers the event content, the intended monitoring workflow, the response-level coverage information, the historical limitation, and the cost. An agent has enough context to decide whether to call it and what the response will convey.

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?

There is only one optional parameter, since, and the schema already describes its format, default, inclusiveness, and archive-start limitation, so description coverage is effectively 100%. The tool description mainly restates that events are returned 'since a date' and the archive caveat, adding no new parameter-level semantics beyond the schema.

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?

The description opens with a specific verb and resource: 'Chronological feed of rating actions since a date,' then enumerates the covered event types (grade upgrades/downgrades, payTo wallet changes, listing removals, returns). This clearly differentiates it from sibling tools like endpoint_credit_score or revenue_estimate, which are point-in-time scoring tools rather than a historical feed.

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?

It gives an explicit use case: 'Use this to monitor a portfolio of endpoints for adverse changes rather than re-scoring each one,' which names the alternative approach (re-scoring) and the condition that chooses this tool. The archive-start caveat also informs when the feed can be used for historical windows.

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