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

Annotations already declare readOnly, idempotent, and non-destructive behavior, so the description doesn't need to repeat those. It adds valuable extras: that no API key is required and that content accuracy is not guaranteed. It also discloses that the word is shared for a given date, which is subtle behavioral context. This goes beyond the annotations without contradicting them.

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?

Two short sentences with no filler. The primary action is front-loaded, followed by the date-sharing behavior and two caveats (auth, accuracy). Every clause adds information; nothing is redundant.

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 simple read-only tool with a single optional parameter, the definition is largely sufficient. It explains the retrieval target and gives a caveat about data quality. The main gap is that it mentions 'available fields' without specifying what those are, and with no output schema the agent lacks return-structure detail. However, this is a minor gap for such a simple tool.

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?

With 100% schema description coverage on the single optional `date` parameter, the schema already documents the format and default. The description references the date concept but adds no syntax or formatting details beyond the schema. This matches the baseline of 3 for high schema coverage.

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 states a specific action: retrieve the stored daily word, with a date qualifier. 'The selected word is shared for a given date' helps distinguish it from general lookup tools among the siblings, but it doesn't explicitly name any alternative. It is not a tautology and gives enough specificity to understand the resource being accessed.

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 this tool (when you want the word of the day), but it does not explicitly state exclusions or alternatives. The sibling list includes many lookup/search tools, yet no guidance is given for when to prefer this over lookup_word or search_words. The 'No API key is required' note is a usage condition, not a routing rule. Usage context is present but inferred.

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