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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the safety profile is covered. The description adds value beyond them by disclosing that there is no upstream dependency and that one call per conversation suffices, which is genuine caching/behavioral guidance.

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 payload contents and ending with the operational note. The middle enumeration is long but each item earns its place by telling the agent exactly which filter vocabularies are available.

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?

With no output schema, the description carries the burden of explaining returns, and it does: it lists the categories of values plus usage notes and example calls. For a zero-parameter reference tool with annotations covering safety, nothing material is missing.

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 tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The description's enumeration of returned value categories compensates for the absent output schema rather than documenting inputs.

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 resource and scope: the vocabulary of filter values (states, cities, qualification groups, AQF levels, field-of-education codes, provider types, education types, sort values, studentLocation semantics) for search_courses. It names the sibling it serves, so an agent can distinguish it from get_course/get_school/search_courses without opening a schema.

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?

Explicitly ties usage to search_courses and states the operational context ('No upstream call; safe to call once per conversation'), which tells the agent when this is cheap and appropriate to invoke. It stops short of stating when NOT to use it or naming an alternative reference tool, but the routing to search_courses is clear.

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