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

With no annotations, the description carries the full burden and does meaningful work: it discloses that the output is a list of candidate headwords, not a single translation, and enumerates the returned fields (score, part of speech, gloss, URL). It does not mention result limits, scoring semantics, or empty-result behavior, which keeps it short of a 5.

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?

A single front-loaded sentence that covers input, matching rule, and return fields with no filler. Nothing could be removed without losing 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?

There is no output schema, and the description compensates by naming the returned fields and the page URL, which is exactly what an agent needs to interpret results. Minor gaps remain around ranking semantics and result size limits for what is likely a fuzzy search.

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?

Only one parameter and the schema already documents it at 100% coverage, so the baseline is 3-4. The description adds value with concrete examples (king, ship, write) that clarify the expected input domain better than the schema's lone 'cyning' example, which is arguably an Old English rather than modern English form.

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: list Old English headwords whose definitions mention a given modern English word, and it clarifies the matching mechanism (definition mention, not direct translation). It distinguishes itself in spirit from lookup_headword by describing the reverse lookup direction, but never names that sibling explicitly.

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?

Usage is implied by 'Given a modern English word...' and the input examples, so an agent can infer the call pattern. However, there is no explicit guidance on when to prefer this over lookup_headword or identify_form, and no note that results are ranked candidates needing disambiguation.

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