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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds that results are ranked by shared muscle involvement, which is real behavioral value, but it says nothing about what happens when no alternatives exist, whether results are capped by the plan (the schema hints at plan caps), or the shape of the returned list.

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 front-loaded sentences with zero filler — the core purpose first, then the optional filtering capability.

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 read-only lookup with 6 mostly-documented parameters and no output schema, the description plus schema covers what an agent needs to invoke it. The remaining gaps (return shape, empty-result behavior) are minor for this tool class.

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 83%, so nearly every parameter is already documented in the schema, including comma-separated syntax for both equipment filters. The description only restates that equipment can be required or excluded; it adds nothing on id, lang, limit, or the undocumented model parameter.

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 (exercise alternatives / 'swaps') and a meaningful criterion ('train the same muscles'), which is more precise than generic similarity. It never names the near-duplicate sibling find_similar_exercises, so an agent must guess which of the two 'related exercise' tools to pick.

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?

'e.g. when equipment is missing' gives a concrete triggering scenario, and 'Optionally require or exclude equipment' tells the agent how the filters are meant to be used. There is no when-not guidance and no explicit routing away from find_similar_exercises or search_exercises.

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