write_custom_exercise

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

Annotations declare destructiveHint=true, readOnlyHint=false, openWorldHint=true. The description adds useful behavioral context: names must be unique among all exercises (a mutation constraint), and the exercise integrates into routines/workouts/stats. However, it doesn't mention what happens to existing fields not provided on update, or the deletion side-effects. Since annotations already carry the safety profile, this added context merits a 3.

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?

The description is compact and front-loaded with the primary create/update distinction first, then integration behavior, then muscle naming, then constraints. Each sentence carries useful information. It could be slightly more structured but is efficient.

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 10-parameter mutation tool with destructiveHint=true and no output schema, the description covers the create/update modes, name uniqueness, target default, and cardio behavior. But it leaves several semantics (equipment/bodyPart effect, how updates merge with existing fields, whether all params are optional) to inference, and doesn't explain what a successful write returns. Adequate but with notable gaps.

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 only 30%, so the description must compensate. It does explain that 'target is the main one (default the first primary)' and that muscles use the app's body-map names, and that cardio exercises log time and speed. But it doesn't explain semantics for equipment, bodyPart, assisted, primaryMuscles vs secondaryMuscles, or the url null behavior. Some compensation but incomplete against the low coverage.

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 clear specific verb+resource: 'Create a custom exercise (no id) or change one (id).' It distinguishes the upsert modes (create vs. update by presence of id) which is genuinely useful. It doesn't explicitly distinguish itself against the sibling delete_custom_exercise, but it's clear enough.

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 gives clear context on how to use it (create without id, update with id) and notes it works like any built-in exercise. It doesn't explicitly state when NOT to use it or name delete_custom_exercise for removal. This is clear usage context but not comprehensive exclusion guidance.

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