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

With no annotations, the description carries the full behavioral burden, and it does so well: it declares the tool is free, has no side effects, does not evict the cache, and does not touch relays. These are exactly the traits an agent needs before making a paid-call decision. It stops short of 5 only because it says nothing about latency or failure semantics.

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?

Three tightly packed sentences with zero waste. The core purpose is front-loaded, followed by the usage rationale and the safety profile — a well-ordered structure.

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 no explanation, and the description covers cost and side effects adequately. It is nearly complete; only minor runtime behavioral details are absent.

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% and both parameters (dpop_token, patron_npub) are documented in the schema itself, so the baseline is 3. The description adds no format or provenance detail beyond what the schema provides.

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: checking whether a cached dpop_token is still valid. It also situates itself relative to the npub-proof flow and the analogous check_oauth_status, so an agent can distinguish it from request_npub_proof, receive_npub_proof, and the payment/status siblings without opening the schema.

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 clear when-to-use context: call it before a paid call to confirm the dpop_token will be accepted 'before burning credits on a guaranteed failure.' It names the analogous check_oauth_status pattern but does not give explicit when-not conditions, so it falls just short of a 5.

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