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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds genuinely new behavior: case-insensitive exact matching against a catalog plus the user's custom exercises, and suggestion generation (up to 3 close matches) for invalid entries. It does not mention the 50-name cap, which is minor.

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?

Three tight sentences: what it checks, the input constraint, and the return contract, in that order. Nothing redundant and no preamble.

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-value documentation is not required, yet the description still names the key fields (all_valid, invalid names, suggestions). Combined with annotations covering the safety profile and a fully documented single parameter, an agent has everything needed to call it correctly.

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 coverage is 100% with a single well-documented parameter, so the baseline is 3. The description earns above baseline by clarifying that the strings must be exact display names and that matching is case-insensitive, which the schema description ('Exercise display names to validate') does not convey.

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 (validate/check) and resource (exercise names) with explicit scope: existence in the catalog or the user's custom exercises. This cleanly separates it from siblings like search_exercises or get_exercise_history without opening their schemas.

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?

Implied usage is clear (pre-flight validation before referencing exercise names), and it notes names must be exact display names. However, it never states when to prefer this over search_exercises, nor any prerequisite such as needing names in hand first, so usage is inferred rather than directed.

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