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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description adds genuinely new behavioral detail: it resolves everyday aliases (RDL, press-up) and explains the shape of the muscles result (muscles.main vs muscles.also, hand-checked for main lifts), which is valuable since there is no output schema.

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?

Purpose is front-loaded in the first sentence, followed by usage examples, then alias handling and result structure. Four short clauses and no filler; only mild redundancy between the title and the opening sentence.

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 single-param read tool with no output schema, the description adequately covers input tolerance (aliases) and the key return fields (muscles.main/also). Annotations carry the safety profile, so nothing critical is missing, though the promised picture/instructions return is not described.

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% for the single 'name' parameter, giving a baseline of 3. The description exceeds that by disclosing that informal names like RDL or lat pulldown are understood, which tells the agent the parameter tolerates aliases rather than requiring canonical names.

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?

Opens with a specific verb+resource: fetch how to do one exercise, its worked muscles, and a picture. The phrase 'one exercise' implicitly contrasts with the sibling list_exercises, but no sibling is named explicitly, so it stops short of a 5.

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 'Use for ...' clause supplies three concrete example questions that define the intended query shape, which is clear context. However it gives no when-not-to-use guidance or alternatives (e.g., list_exercises for browsing all moves), so it lacks explicit routing.

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