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

Annotations already cover the safety profile (readOnlyHint, idempotent, non-destructive), yet the description adds real behavioral value: return shape, the in_plans cross-reference, and the optimistic-concurrency contract where updated_at must be passed as base_updated_at or the edit is refused. That last point is non-obvious and operationally important.

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?

Three densely packed sentences, front-loaded with the usage trigger followed by return contents and the edit_routine handoff. No filler; each sentence carries distinct information.

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 needn't be explained, and the description goes beyond that with filtering rules and the concurrency contract. The only gap is the undocumented `limit` parameter, which an agent may need to understand for large result sets.

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 must carry the load, and it explains routine_id filtering, name search, and the omit-both-for-all default. However, the `limit` parameter is never mentioned in the description or schema, leaving one of three parameters undocumented.

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 ('Returns routines') with explicit scope ('in any plan or none') and details the returned content (exercises, default_sets, notes, in_plans with day_of_week). This clearly distinguishes it from edit_routine and save_routine among the siblings.

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?

Gives a concrete trigger ('when the user asks about their saved routines') and a workflow role ('before changing one'), and routes the mutation to edit_routine via base_updated_at. It lacks explicit when-not guidance versus siblings like get_training_plan or get_exercise_library, so it falls 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.