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

Annotations already declare destructiveHint=true and idempotentHint=true, so safety is partly covered. The description adds meaningful behavior beyond them: changes are 'applied at once, with no confirmation step', only changed fields should be sent (partial update), and built-ins return a not_custom outcome. It stops short of describing any rate limits or full validation error surface.

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?

Front-loaded with the triggering condition, then slug lookup, then mutable fields, then the no-confirmation caveat. Dense and largely waste-free, though packing the slug-validation parenthetical and the post-edit sentence into one block slightly dilutes scanability.

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 description covers trigger, prerequisite, mutable fields, and the no-confirmation behavior. The only gaps are the unexplained 'reasoning' parameter and the exact required-vs-optional framing for the mutation body.

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 0% schema description coverage, the description carries the burden and does: it enumerates the mutable fields (name, muscle_groups, equipment, type, unilateral, notes) and clarifies notes is the step-by-step how-to, one step per line. It does not explain the 'reasoning' parameter or explicitly tie exercise_slug to the required-key role.

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 names a specific verb set (rename, re-file, rewrite the how-to) and a precise resource scope (one of their OWN custom exercises). It distinguishes from built-ins and points to get_exercise_library, so an agent can tell it apart from add_custom_exercise or set_exercise_note without opening a schema.

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?

Explicit when-to-use ('when the user asks to rename/re-file/rewrite' or 'has just agreed to it') and a clear exclusion rule ('only is_custom: true rows qualify; built-ins return not_custom'). It also names the prerequisite tool (get_exercise_library) to obtain the slug.

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