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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety behavior is covered. The description adds the delivered outputs (5K splits, halfway, final pace), but that largely duplicates the existing output schema rather than adding behavioral context like rounding rules or what happens for off-distance races.

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 short sentences, front-loaded with the primary purpose. The trailing 'See list_bundles...' pointer is marginal but compact. No filler or repetition.

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?

The tool is simple, read-only, with an output schema, so return-value detail is optional. The remaining gap is the phantom 'distance km' input, which leaves the description inconsistent with the actual single-parameter contract.

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%, which would normally justify a baseline of 3. But the description asserts inputs of 'target finish time, distance km,' while the schema contains only target_time_minutes with no distance parameter. Advertising a nonexistent input misleads the agent about how to invoke the tool.

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: 'Generate target split times for a marathon, half-marathon, or other race.' This distinguishes it reasonably from neighbors like calculate_running_pace or calculate_race_prediction. However, it does not name an alternative sibling, so the differentiation is implicit rather than explicit.

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?

'Use for race-day pacing' gives a clear context, but there is no when-not guidance and no routing to alternatives such as calculate_running_pace or calculate_race_prediction, which an agent would need to disambiguate a large family of running calculators.

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