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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint, so safety is covered. The description adds genuine value beyond them: the 'Free' cost signal, the fact that no source records are returned, and the semantic caveat 'Reachability is not completeness,' which guards against over-reading the result.

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?

Three short sentences, front-loaded with the cost and purpose, then the routing alternative, then the caveat. No filler; every sentence carries a distinct fact.

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-value detail is not required, and the description supplies the cost, non-return semantics, and a caveat on interpretation. Only minor gap is no note on failure behavior when a source is unreachable, which would round out the reachability probe.

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 each parameter (city, state, jurisdiction_id) is already documented with its pairing and precedence rules in the schema. The description adds nothing about parameter usage, so the baseline 3 applies.

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 ('Probe registered official-source reachability for a jurisdiction') and immediately scopes it ('without returning source records'), which separates it from sibling catalog/coverage tools. The distinction from get_source_catalog is named explicitly, so an agent can route without opening schemas.

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?

Explicit when-to-use ('Use this for current source availability') paired with a named alternative and its condition ('use get_source_catalog for source identity and freshness expectations'). This is the clearest form of routing guidance.

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