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

Annotations already declare destructiveHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely non-obvious behavior beyond that: partial payloads trigger a fetch-and-merge against current workout data. It omits the flip side — that supplying instances or category_ids appears to replace those collections wholesale — which matters given the destructive hint.

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 sentences, front-loaded with the action, then the usage trigger and the merge caveat. No filler. Slightly compact for an 8-parameter mutation, 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?

An output schema exists, so return values need no explanation, and the merge behavior is a useful addition. Still, for an 8-param destructive mutation with zero schema descriptions, the definition leaves key fields (workout_id, team_id, category_ids) and the replace-vs-merge semantics of arrays unexplained.

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 description coverage is 0%, so the description must carry all parameter meaning, and it only partially does. It names name, description, difficulty, visibility and "exercise structure" (instances), but never explains the required workout_id, team_id, or category_ids, nor whether array fields replace or merge.

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 ("Updates an existing workout") and enumerates the mutable surface: name, description, difficulty, visibility, exercise structure. That is enough to distinguish it from update_program, update_drop, and update_exercise_group by resource, though it never names a sibling explicitly.

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?

"Use when the user wants to change ..." gives a concrete trigger condition tied to user intent. It does not cover when-not cases or route to alternatives such as adapt_workout for adaptive changes or create_workout for new workouts, so it stops short of full routing guidance.

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