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

Annotations already declare readOnlyHint=true and openWorldHint=false. The description adds 'cost: free (pure CPU, no network)' and 'static' to reinforce non-mutating behavior, plus details about mapping to RFC anchors and operator causes. No contradiction with annotations.

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 well-structured: a cost/read-only note, a clear statement of what the tool does, an input instruction, and pairings with alternatives. It is front-loaded and every segment earns its place, staying compact without sacrificing useful details.

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?

The description covers inputs, purpose, and relationship to siblings, which is sufficient for an agent to decide when to invoke it. Minor gap: no output format is described, but for a static explainer with no output schema this is not a significant deficiency.

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 has 100% coverage with both parameters described ('Attestation level: A Full / B Partial / C Gateway' and 'SIP response code commonly seen in STIR/SHAKEN flows'). The description adds the either/or usage rule and RFC 8588 context, but the schema already carries the core meaning, so baseline 3 is appropriate.

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 clearly identifies the tool as a 'static explainer' that maps attestation levels (A/B/C) and SIP codes to plain-English explanations. It distinguishes from siblings by explicitly noting it is not a validator and pairing it with validate_stir_shaken_identity for cryptographic verdicts.

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 clear guidance: 'Provide either attestation or code' and names two sibling tools with specific use cases (validate_stir_shaken_identity for JWS verification, search_sip_docs for ATIS/CTIA/RFC depth). Lacks explicit 'do NOT use when' exclusions, but the pairings effectively communicate scope.

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