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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds the grouping behavior and the downstream consequence ('Canonical names ensure proper exercise tracking and NSI score calculation'), which is useful context. It does not describe pagination or ordering, but for a zero-parameter catalog read this is a reasonable level of disclosure.

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 sentences, all informative and front-loaded with the core behavior. The second sentence is a compact usage rule, and the third explains the rationale. Minor redundancy exists between 'canonical exercise names' and the final sentence, but nothing is wasted.

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 zero-parameter, read-only, idempotent catalog tool with an output schema, the description covers the essential decision points: what it returns, when to call it, and when not to. It does not detail the output schema structure, but the output schema itself carries that burden. The only minor gap is not naming a specific sibling alternative, though the usage rule makes the boundary clear.

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 has zero parameters, so the schema provides no parameter semantics to rely on. The description compensates by clarifying what the returned data represents (canonical exercise names grouped by muscle group) and why that matters. There is no parameter ambiguity to resolve.

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?

The description states a specific verb ('Returns'), a specific resource ('canonical exercise names from the exercise library'), and a grouping dimension ('by muscle group'). It clearly distinguishes this from the many list_* siblings by focusing on the exercise catalog rather than user logs or metrics.

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 explicitly says when to use it: 'before logging, adding or renaming exercises when canonical names are not already known.' It also gives an exclusion: 'Metadata/set-value edits: no catalog lookup.' This is strong routing guidance relative to the large sibling set.

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