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

Annotations already declare readOnly, idempotent, closed-world, non-destructive behavior, so the safety profile is covered. The description adds genuinely new behavioral context by disclosing the Riegel formula and the exact return fields, which helps the agent understand the computation's assumptions.

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 tight sentences, front-loaded with the purpose and method. The 'Returns: {...}' clause is largely duplicative of the existing output schema, so it does not fully earn its place, but there is no padding or rambling.

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 full schema coverage, complete annotations, and an output schema, the description only needs to cover purpose and method, which it does. It omits Riegel formula caveats (e.g., applicability range, exponent assumptions) and sibling routing, but those gaps are minor given the rich structured metadata.

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% and each of the three required parameters is documented in the schema itself. The description adds no parameter-level meaning (e.g., valid ranges or that reference_distance/time must correspond to a prior race result), 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?

States a specific verb (predict) and resource (race time for a target distance) and names the underlying method (Riegel formula), so an agent knows exactly what computation happens. It does not name a specific sibling such as calculate_running_pace or calculate_marathon_splits, so it falls short of full sibling differentiation.

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?

There is no explicit statement of when to use this tool versus alternatives like calculate_running_pace, calculate_marathon_splits, or calculate_vo2max. The 'See list_bundles' pointer is a discovery hint, not usage guidance or an exclusion condition.

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