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

Annotations already declare this is a non-destructive write with openWorldHint, so safety is largely covered. The description adds one genuinely non-obvious behavior – an empty list means every week – but does not say whether sessions already planned in weeks that get dropped survive the call, which is the key risk for a mutation like this.

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?

A single front-loaded sentence with the primary action first and the edge case after a semicolon. No filler to trim.

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 small, well-annotated two-parameter mutation with no output schema, the core is present. What's missing is side-effect disclosure: whether existing planned weeks/sessions are removed, and confirmation of replace-versus-append semantics of '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?

Schema coverage is 100%, so both parameters are documented in the schema (including the Monday YYYY-MM-DD format). The description nonetheless adds meaning the schema lacks: the empty-array edge case from week_start_dates.

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 and resource – what is being set (the planned weeks of a workout) – which is clear enough to distinguish the write operation from the read-side sibling get_workout_weeks. It stops short of naming or contrasting with any sibling explicitly.

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?

Usage is implied: replace the week schedule of an existing workout. There is no explicit statement of when to use this versus get_workout_weeks or update_workout, and no prerequisites (e.g. workout must exist) are given.

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