mcmillan_heart_rate_zones

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

With no annotations provided, the description carries the full burden. It discloses key behavioral traits: it performs calculations (not destructive), uses estimation formulas when max_heart_rate is not provided, and returns a dictionary with specific outputs. However, it lacks details on error handling, performance characteristics, or rate limits.

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?

The description is efficiently structured: a clear purpose statement, methodology details, parameter explanations, and return value description—all in four concise sentences with zero wasted words. It's front-loaded with the core functionality.

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?

Given the tool's moderate complexity (3 parameters, calculations with multiple methods), no annotations, but with an output schema (implied by 'Returns' section), the description is largely complete. It covers purpose, parameters, methodology, and outputs. Minor gaps include lack of error cases or example usage.

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 0%, so the description must compensate. It clearly explains the meaning of all three parameters (age, resting_heart_rate, max_heart_rate), including units (years, BPM) and the optional nature of max_heart_rate with its estimation behavior. This adds significant value beyond the bare schema.

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 specific action ('Calculate heart rate training zones'), the methodology ('McMillan methodology'), and the required inputs ('based on age, resting heart rate, and optional max heart rate'). It distinguishes itself from sibling tools by focusing specifically on heart rate zones rather than pace, velocity, or race time predictions.

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 usage when heart rate zones are needed, mentioning the McMillan methodology and alternative calculation methods (HRMAX and HRRESERVE). However, it doesn't explicitly state when to use this tool versus its siblings (like mcmillan_calculate_training_paces) or provide clear exclusions or prerequisites.

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