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

Annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=false, so the safety profile is fully carried by structured data. The description adds only the return content ('ports, endpoints, services, links'), which is genuinely useful in the absence of an output schema but is not deep behavioral context. A 3 is appropriate given the annotations do the heavy lifting.

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, all front-loaded: purpose plus contents first, then scope exclusions, then the routing rule. Nothing is repeated and every clause carries new information.

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-enum lookup tool with annotations covering safety, the description supplies the two things not in structured data: the scope boundary and a sketch of the returned reference. Without an output schema, a slightly fuller picture of the returned shape would be ideal, but an agent has enough to call this correctly.

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 parameter's enum is self-documenting, which sets the baseline at 3. The description adds value by rendering the enum values as human-readable API names ('Token Standard APIs', 'Splice HTTP'), helping match those to how a user phrases the request. It stops short of clarifying ambiguous cases between similar APIs, so it is a modest gain, not a full one.

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 ('Get a structured reference') and enumerates exactly what the reference contains (ports, endpoints, services, links) and which seven APIs are covered. It explicitly rules out GitHub, REST, and non-Canton APIs, so an agent can separate it from the many doc-fetching siblings without opening the 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?

Gives an explicit trigger ('use when the user names one of these Canton APIs') and names the alternatives for the other case ('use search/semantic_search for broader doc lookups'). Negative scope is also stated ('Not for GitHub, REST, or non-Canton APIs'), so both the when and the when-not are covered.

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