update_activity

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

Goes well beyond the destructiveHint annotation: it discloses that only given fields are sent (PUT /activity/{id}), that name and description REPLACE existing text, that an empty description is ignored, that at least one field is required, that dry_run previews, and that Strava imports fail. This is exactly the mutation-specific context annotations cannot convey.

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 gating condition is front-loaded and every subsequent sentence carries operational weight (replacement behavior, field requirement, Strava exclusion, return values). No filler despite the density.

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 output schema, it still describes the return ('stored values and the activity summary') and covers preconditions, replacement semantics, and failure modes. An agent has everything needed to call it correctly and safely.

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 the baseline is 3. The description adds real meaning beyond the schema: replacement semantics for name/description, the fact that an empty description is ignored, and clear_description's purpose of deliberately emptying text, which clarifies how these parameters interact.

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: writes RPE, feel, name or description of one activity to Intervals.icu. It distinguishes itself from siblings by routing notes to add_activity_message, so an agent can pick between the two without opening schemas.

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?

Explicit gating: 'Use only when the athlete asks to rate, rename or describe an activity.' It names the alternative for a different need (Notes go to add_activity_message) and states an exclusion (Strava-imported activities cannot be updated).

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