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

With no annotations provided, the description takes on the burden. It clearly states 'Free, no side effects — does not evict the cache or touch relays,' which is valuable safety information. It doesn't explain potential edge cases like missing tokens or cache misses, but for a simple check tool the disclosed behavior is largely sufficient.

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: purpose, use-case, and safety. It is front-loaded with the main action, every sentence adds distinct value, and there is no redundant text.

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?

Given the tool's low complexity, the description covers purpose, usage scenario, side-effect safety, and its relationship to a sibling tool. The input schema is fully documented and an output schema exists, so the description provides sufficient context for an agent to select and invoke this tool effectively.

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 param semantics beyond the schema, only implying the dpop_token is used for paid calls. It does not elaborate on parameter formats or relationships beyond what the schema already documents.

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 the sibling 'check_oauth_status' by stating it mirrors that tool but for the npub-proof flow, making the purpose unambiguous.

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?

Explicitly provides usage context: 'a calling agent can ask "will my next paid call accept this dpop_token?" before burning credits on a guaranteed failure.' It also mentions the alternative 'check_oauth_status' and positions this tool as the right choice for the npub-proof flow, offering both when-to-use and exclusion guidance.

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