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

With no annotations, the description carries the full burden but does disclose meaningful traits: cost ('Free'), key algorithm (RS256), that keys are public, and that sandbox uses a separate key set. It omits caching/rotation and rate-limit behavior, which matter for a JWKS endpoint, so it is not complete.

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?

Two tightly packed sentences, front-loaded with what the endpoint returns and followed by the sandbox caveat. No filler or redundant restatement.

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 single-parameter, no-output-schema key-fetch tool, the description covers purpose, cost, and the sandbox variant, which is sufficient to call it correctly. Naming it a JWKS implicitly conveys the return shape, though the exact response format is not spelled out.

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 the single param is already documented with its issuer value in the schema. The description restates the sandbox behavior and adds only that sandbox keys sign sandbox assertions, so it clears the baseline without adding much beyond the schema.

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 resource (public RS256 keys) and its use (verify an assertion_token locally), which is concrete and actionable. It does not differentiate itself from the nearby sibling identity_get_test_key, so it stops short of a 5.

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 implied context ('to verify an assertion_token locally') and a routing hint for the sandbox variant, plus a cost note ('Free'). It never states when to prefer this over identity_get_test_key or identity_status, leaving sibling selection to inference.

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