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

No annotations are provided, so the description must disclose behavioral traits. It states the tool calculates zones and mentions the Karvonen option, but does not mention that it is read-only or any assumptions about inputs or output format. For a simple calculator, this is adequate but not outstanding.

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: the first delivers the core purpose and method variant, the second directs to related calculators. No redundancy, front-loaded, every word serves a purpose.

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 calculator with an output schema, the description is complete enough: it explains the calculation and method variant. It could optionally describe the return format, but the output schema covers that.

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?

Input schema has 100% description coverage, but the description adds value by relating the optional resting_hr to the Karvonen method, making the parameter's role clearer beyond the schema's technical constraints.

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 clearly states the tool calculates heart rate training zones Z1-Z5 and specifies the Karvonen method as an option, distinguishing it from siblings like calculate_max_heart_rate and calculate_training_zones_running.

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?

The description implies use for heart rate zone calculations with optional Karvonen method but does not explicitly state when to use or avoid this tool versus alternatives. The reference to list_bundles for related calculators provides indirect guidance.

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