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

Annotations already cover readOnly/idempotent/non-destructive, so the bar is lower. The description adds real value by disclosing that it understands everyday aliases (RDL, press-up, lat pulldown) and that results structure muscles.main vs muscles.also, which the annotations do not convey.

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?

Reasonably front-loaded, but the leading 'Plan My Workout. How to do one exercise, the muscles it works and a picture.' largely restates the title, adding duplication without new information. The alias and muscles.main/also content is the part that earns its place.

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?

No output schema exists, so the description carries the return-shape burden and does so for the muscles fields (main/also). It is essentially complete for a single-param lookup, though the promised 'picture' is never described in form or format.

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?

With 1 param at 100% schema coverage the baseline is 3, but the description adds meaningful semantics beyond the schema: the tool accepts informal exercise names and nicknames, so callers know flexibility in the 'name' value is allowed.

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+resource: returns how-to, muscles worked, and a picture for ONE exercise, which implicitly separates it from planmyworkout_list_exercises and get_workout_plan. It does not explicitly name or differentiate from those siblings, keeping it just 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?

Provides the 'Use for' cue plus concrete example questions ("how do I do a Romanian deadlift?"), which gives implied usage context. However, it never states when not to use it or nudges toward siblings like list_exercises, so guidance remains inferred rather than explicit.

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