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

The description adds context beyond annotations by stating the tool is 'deterministic' and detailing the return fields (definition, part of speech, example, synonyms/antonyms). Annotations already indicate readOnlyHint, idempotentHint, etc., and the description aligns with them without contradiction.

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 concise (3 sentences) with front-loaded purpose. Every sentence adds value: usage context, return details, and an explicit alternative. No extraneous 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 simple read tool with one optional parameter and no output schema, the description covers purpose, usage guidelines, return fields, alternatives, and parameter scope comprehensively. It is complete for the given complexity.

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 input schema already has 100% description coverage for the only parameter 'test_family', listing valid values. The description merely restates that it's 'optionally scoped to a test family' without adding new semantics, meeting the baseline 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 that the tool returns today's Word of the Day with specific fields (definition, part of speech, example, synonyms/antonyms). It explicitly distinguishes itself from the sibling tool 'get_definition' by stating 'Do not use for arbitrary lookups — call get_definition instead.'

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 provides explicit usage guidance: 'Use this when the user asks for today's word, a daily vocabulary nudge, or a single-word warmup.' It also clearly states when not to use it and directs to 'get_definition' for arbitrary lookups, providing clear alternatives.

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