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

Annotations already declare a non-read-only, non-destructive, closed-world write. The description adds one piece of genuinely new behavior — that the call also marks the task done, i.e. a side effect beyond the recorded time. It does not say what happens if a time was already logged (overwrite? error?), which is the main residual risk for a write tool.

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?

Two sentences, front-loaded with the primary action and ending with the conditional case; every clause carries information and nothing is padded.

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 low-complexity three-parameter logging tool with full schema coverage, annotations, and no output schema, the description covers the main/interval distinction and the completion side effect. It is only slightly incomplete in not covering repeat-submission behavior.

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 description coverage is 100%, so task_id, time, and rep_number are already documented with format and bounds. The description adds the semantic condition for rep_number (only on interval days, logs one interval) and reinforces the MM:SS/seconds format, but this largely restates the schema, so the baseline 3 applies.

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 gives a specific verb+resource: logging the elapsed time of "today's cardio main task (the timed swim or run)" and marking it done, which distinguishes it from generic exercise logging. It stops short of naming a sibling (e.g. log_exercise) to contrast against, so it is clear but not fully differentiating.

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 rather than stated: it applies to today's cardio main task, with a conditional branch ("For an interval day, pass rep_number") that tells the agent which parameter to set in that case. There is no explicit when-not guidance or named alternative for logging non-cardio or non-main work.

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