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

With no annotations provided, the description carries the full burden and compensates well: it explicitly states 'Free, no side effects — does not evict the cache or touch relays' and clarifies the token is 'previously-sached.' This goes beyond a plain 'check' by disclosing the non-destructive, cached-read behavior, though it does not detail failure modes or what happens on invalid tokens.

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 tight and front-loaded: the first sentence states the exact purpose, the second adds the high-value use case and sibling comparison, and the third discloses cost/side effects. Every sentence earns its place, with no fluff or repetition of schema fields.

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 two-parameter read-only check with an output schema present, the description is largely complete: it explains purpose, usage context, cost, and side-effect absence. It does not describe the output format, but that is covered by the output schema. Minor missing context includes whether the check requires any prior authorization or how staleness/interaction with the cache is handled, but these are not critical for an agent deciding to invoke it.

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?

Schema description coverage is 100%, so the baseline is 3. The description adds minimal parameter context beyond the schema: it only reinforces that dpop_token is previously-sached and part of the npub-proof flow, and does not mention patron_npub at all. That is acceptable since the schema already describes both parameters accurately.

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: 'Check whether a previously-cached dpop_token is still valid.' It clearly distinguishes itself from sibling tools by scoping to the npub-proof flow and explicitly names its sibling analog ('Mirrors check_oauth_status'), so an agent can tell it apart without opening schemas.

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?

The description gives a clear usage scenario: an agent can ask if the next paid call will accept this dpop_token before burning credits. It names the alternative flow (check_oauth_status for npub-proof vs OAuth) and states the tool is free, helping with when-to-use decisions. It doesn't enumerate exclusions, but the context is strong.

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