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

No annotations are provided, so the description carries the full behavioral burden. It does disclose the confirm-gating behavior and the data-sourcing pattern (carry over exerciseId from the catalog), which is useful, but it says nothing about permissions, whether the displaced exercise is recoverable, or what the preview/response contains.

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 tightly packed sentences with the core purpose front-loaded, followed by the alternative and the parameter-sourcing hints. No filler, no repetition of the schema.

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 mutation tool with no annotations, no output schema, and a nested untyped object, the description supplies the role, the confirm gate, and where each parameter value comes from. It omits authorization requirements and the exact preview/return shape, but the essential path to a correct call is present.

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 only 25% (only confirm is described) and newExercise is an opaque nested object, so the description must compensate. It explains exerciseOrder as the slot's `order` sourced from list_workout_plans and defines newExercise by reference to the create_workout_plan shape plus the exerciseId carry-over rule. planId and the confirm preview semantics remain undocumented in the description, keeping it below 5.

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 ('Replace a single exercise in a workout plan by its order') and immediately differentiates itself from the sibling update_workout_plan as 'the surgical alternative'. An agent can distinguish it from create_workout_plan, update_workout_plan, and swap_diet_meal without opening any 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?

Names the alternative (update_workout_plan) and the selection logic (surgical single-slot change vs. whole-plan update), and routes the agent to list_workout_plans for the order value and search_exercises for exerciseId. No explicit 'do not use when...' exclusion, so it stops just short of a 5.

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