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

Annotations already declare read-only, idempotent, non-destructive behavior. The description adds valuable context beyond that: graph coverage varies, an empty result is valid, a key is required, and calls count toward quota. This helps the agent set expectations and handle empty responses correctly.

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, each carrying essential information: core operation, edge-case expectation, and auth/quota caveat. No filler or repetition of schema 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?

For a one-parameter read-only tool, the description covers the operation, the possibility of empty results, and the authentication requirement. Without an output schema, a bit more detail about the response shape would be ideal, but the description is sufficient for correct invocation.

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?

The single parameter 'word' is fully described in the schema (100% coverage), so the description does not need to add much. It only reinforces the idea of tracing through the graph, which is marginal value 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?

Names a specific verb ('retrieve') and a specific resource ('existing links between an English headword and lessons or themes'). This clearly distinguishes it from the lookup/search siblings, which operate on definitions, translations, or related words rather than graph links.

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?

The description implies when to use the tool: when graph-based links between a word and lessons/themes are needed. It does not explicitly mention alternatives or exclusion criteria, so an agent must infer selection from the resource description alone.

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