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

Annotations indicate readOnlyHint=false and destructiveHint=false, so the tool performs non-destructive writes. The description adds that archive_routine is reversible and unarchive_routine restores, and explicitly directs destructive operations to another tool. It also mentions bulk support. However, it does not disclose idempotency or error behaviors beyond what annotations imply.

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 lengthy, listing multiple actions with bullet points and static options. The flattened action note is helpful, but the inclusion of many actions under a single tool description makes it less concise than focusing on the add_exercise action. The structure is readable but could be streamlined.

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?

Given the high parameter count and no output schema, the description should explicitly link parameters to actions. It partially does for a few (exercise_id for add_exercise), but fails to cover parameters like instructions, showTrainingTime, or the bulk IDs. The static options only cover four fields; the rest are underdocumented. The description does not specify which parameters are required per action, leaving the agent underinformed.

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?

The schema has 26 parameters with 0% description coverage. The description provides static option mappings for trainingType, goal, difficulty, and day, adding value for those. However, many parameters (e.g., name, reps, rest, weight, allowPdfDownload) are not explained in the context of specific actions, leaving the agent to infer their usage from names alone.

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 says 'Create / update workout routines, sessions, and exercises', which broadly states its purpose. However, the tool name specifically focuses on 'add_exercise', yet the description includes many other actions (create_routine, update_routine, archive, etc.), causing ambiguity about the tool's primary function. The flattened action note hints at add_exercise, but the extra actions dilute clarity.

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 some usage guidance: for destructive operations use mfit_workout_delete, and references mfit_search_exercises to find exercise_id and mfit_workout get_session for serie IDs. However, it does not clarify when to use this aggregated tool versus separate sibling tools like mfit_workout_write_create_routine or mfit_workout_write_create_session, which exist for specific actions.

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