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

Annotations already mark the tool read-only, idempotent, and non-destructive, and the description adds meaningful behavior beyond that: it returns found records, explicit misses, and lookup failures; optional fields and translations vary; requires an Authorization header; and counts against account quota. 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 information-dense and front-loaded, with the core purpose stated first, followed by limits, return behavior, and authentication. The final marketing link ('Evaluate and compare plans at...') is not necessary for invoking the tool correctly, which prevents a 5.

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 read-only batch lookup tool with one required parameter and no output schema, the description is complete: it covers what is returned, how content may vary, authentication, quota, rate limits, and the no-generation scope. An agent has enough context to call it 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?

The schema covers 100% of the parameter semantics, including the word pattern, length limits, max items, and free/paid maxima, so the baseline is 3. The description mostly repeats the headword-count limits and adds a 10-requests/minute rate limit, but adds little new meaning specific to the words parameter.

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 names a specific verb ('Retrieve') and resource ('stored AI-assisted English lexical records for a vocabulary list'), and the modifier 'without generating missing words' distinguishes it from generative tools. The plural 'vocabulary list' separates it from the singular sibling lookup_word.

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 clearly implies when to use the tool: for batch lookup of stored records over a list of headwords, with explicit free/paid limits and a required API key. However, it does not explicitly route the agent to alternatives like lookup_word for single words or search_words for fuzzy matching, leaving some sibling differentiation to inference.

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