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

Annotations already establish readOnly/non-destructive/closed-world, so the safety profile is covered. The description adds genuine behavioral value on the output side: the granularity of data returned (laps, splits, best efforts, PRs, HR zones, totals) and the platform compatibility, which is important since no output schema exists.

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?

Front-loads what the tool returns, then closes with two short, actionable sentences about platform support and id sourcing. The long content enumeration is dense but every item is informative; no filler sentences.

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?

With no output schema and a single required param, the description carries the burden of describing return content and does so thoroughly, plus names the id sources. Minor gaps remain: no mention of behavior when the id is invalid or not found, and no pagination-size caveats, but these are small for a read-only detail fetch.

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?

Only one parameter with 100% schema description coverage, so the schema already defines session_id and its provenance. The description restates the same sourcing hint ('Use the `id` from get_workout_history or get_cardio_summary'), adding no syntax or format detail beyond the schema. Baseline 3 is appropriate.

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 precise verb+resource (fetch one logged session in full) and enumerates the returned detail: per-lap distance/time/pace/HR, km and mile splits, best efforts, PRs, HR-zone minutes, totals. It also names the sibling sources that supply the id (get_workout_history, get_cardio_summary), so an agent can route between this and the summary/history tools 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?

Explicitly tells the agent where the required id comes from (get_workout_history or get_cardio_summary) and notes the platforms it works for (Garmin, Apple Watch, in-app GPS). It gives clear when-to-use context but stops short of stating when to prefer a sibling such as get_cardio_summary or get_recent_runs instead.

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