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

Annotations cover the safety profile (readOnlyHint=true, openWorldHint=false), and the description adds the key behavioral context that this is diagnostic lookup driven by a header value rather than a general audit endpoint. It doesn't state the form of the returned explanation, but as a read-only explainer with no side effects that gap is minor.

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?

One sentence, zero filler, and the purpose is front-loaded before the input source. Nothing should be trimmed.

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 one-parameter read-only tool with no output schema, the definition covers purpose, input provenance, and the nature of the response ('what it means and how to fix it'). Only a hint about the explanation's structure is missing.

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% and the single param is well documented, but the description still adds value by naming the concrete source (the x-gate-refused header) and giving a real example value, disambiguating the free-form string the schema leaves open.

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 (explain) and resource (a Gate refusal), plus what the answer contains: meaning and remediation. The example value 'route_not_allowed' makes the scope concrete and distinguishes it from the sibling gate_* tools that manage apps, runs, and audits.

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?

It tells the agent exactly when this tool applies: when an x-gate-refused header value is present, that value is the input. There is clear context but no explicit statement of alternatives or exclusions (e.g. what to do if no refusal occurred).

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