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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuine behavioral context beyond that: the verbatim-output requirement for employer_acceptance wording and the instruction to redirect enrolment to the url rather than acting.

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?

Front-loaded with the essential identity of the tool and kept to three sentences, each carrying an instruction. The middle enumeration of returned facets is somewhat list-heavy but is not wasted, since it steers what the agent surfaces to the user.

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?

An output schema exists, so return-shape explanation is not required, and the description supplies the two behavioral rules an agent most needs (verbatim wording, url-based enrolment). Minor gaps remain around error/unknown-slug behavior, but nothing essential for correct invocation 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?

Schema description coverage is 100% and the schema already documents both the slug provenance/example and the country default (United States when omitted). The description restates country-driven pricing and cross-country versions but adds no syntax or edge-case detail beyond the schema, 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?

Specific verb+resource (fetch a single course by slug) with an explicit pointer to where the slug comes from (list_courses), which cleanly separates it from the list sibling. It even enumerates the returned facets, so an agent knows exactly what this tool is for.

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?

It states the input source ('from list_courses') and gives two actionable directives (deliver employer_acceptance wording verbatim, send enrolees to the course url), which is real routing guidance. It does not, however, state when to prefer the sibling employer_acceptance tool or what to do if the slug is unknown.

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