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

No annotations are provided, so the description carries the full behavioral burden, and it does well: 'Free, no side effects — touches no relay,' and it discloses that expiry is read from the grant itself while the only store consulted is the patron's revocation watermark. This tells an agent this is a cheap, non-mutating, read-only check. It does not mention auth/permission requirements or failure modes, keeping it short of a 5.

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?

Purpose is front-loaded in the first sentence, followed by rationale and behavior. It is efficient overall, though the RST-style double-backticks and the 'mirrors check_oauth_status' reference add mild noise and point to a tool not present in the sibling set.

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?

An output schema exists, so return values need not be explained. With no annotations, the description compensates by covering cost, side effects, and the data sources consulted. It is complete enough to invoke correctly, with only auth requirements and the referenced non-existent sibling left as minor gaps.

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 coverage is 100%, so both dpop_token and patron_npub are fully documented in the schema, making a 3 the baseline. The description adds marginal value by clarifying that expiry comes from the grant itself and that the patron's revocation watermark is the only consulted store, which slightly enriches understanding of the two inputs.

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?

States a specific verb and resource: 'Check whether a proof grant is still valid.' It further frames the domain with 'for the npub-proof flow' and the concrete question an agent would ask ('will my next paid call accept this dpop_token?'). It distinguishes itself from the many check_* siblings by scoping to the npub-proof grant rather than balance, unlock, or payment state, though it doesn't name the sibling tools it is closest to.

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 a clear when-to-use: call it before a paid call to avoid 'burning credits on a guaranteed failure.' The pre-flight framing makes the context explicit. It does not name an alternative or state an exclusion condition (e.g., when receive_npub_proof or check_unlock is the better choice), so it stops short of full routing guidance.

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