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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=true, destructiveHint=false), so the bar is lower. The description still adds real value beyond them: it discloses the return shape (a text list of every recorded meaning plus a total definition count) and, importantly, a cost of 2 credits, which is a behavioral constraint an agent should weigh before calling.

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 sentences, front-loaded with the core action and with the cost disclosure placed last where it reads as a footnote. Minor waste in the redundant "Dictionary: Dictionary looks up" prefix that restates the name, but nothing else is padding.

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 lookup with an output schema, this covers purpose, return shape, and cost. The only missing piece is differentiation from the many word-related siblings, which matters more here than for most tools given the crowded namespace.

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?

Schema description coverage is 100% for the single `word` parameter, including an example, so the schema already carries the semantics. The description's phrase "any given term" adds no format, casing, or multi-word guidance beyond what the schema states, so the baseline 3 applies.

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?

"Dictionary looks up word definitions for any given term" gives a specific verb (looks up) and resource (word definitions), so the tool's function is unambiguous. It does not, however, distinguish itself from nearby siblings such as Thesaurus, AntonymFinder, WordOpposites, or PartsOfSpeech, which an agent could easily confuse it with.

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 names target audiences (e-readers, vocabulary builders, writing assistants) but that is audience framing, not routing guidance. There is no statement of when to prefer this over Thesaurus or PartsOfSpeech, and no exclusions or preconditions for a 2-credit call.

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