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

With no annotations supplied, the description carries the full behavioral burden and mostly succeeds: it declares the tool is 'Free, no side effects — touches no relay' and discloses exactly which stores are read ('Expiry is read from the grant itself; the only store consulted is the patron's revocation watermark'). It does not mention auth requirements or rate limits, but for a read-only status check this is solid disclosure.

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 core purpose is front-loaded in the first sentence, and the following sentences each add distinct value (the sibling parallel, the motivating use case, the data-source scope, the no-side-effects guarantee). Slightly long but nothing is padding.

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 described. Combined with the schema's full parameter coverage, the description supplies the operational context (free, side-effect-free, reads only the revocation watermark) an agent needs to call it safely. Only minor omissions like auth/error expectations remain.

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 both parameters are already documented (dpop_token as the grant envelope, patron_npub as the npub). The description reinforces the token's role in the flow ('will my next paid call accept this dpop_token?') but adds no format, syntax, or edge-case detail beyond the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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') and immediately distinguishes itself from the sibling excalibur_check_oauth_status by naming it as the parallel for the npub-proof flow. An agent can tell this apart from other check_* tools without opening any 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?

Provides a concrete usage scenario ('ask "will my next paid call accept this dpop_token?" before burning credits on a guaranteed failure'), which tells the agent exactly when to reach for it. It lacks an explicit when-not condition or named alternative for the adjacent flow, so it stops 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.