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

Annotations already declare the tool as read-only, idempotent, and non-destructive. The description adds valuable behavioral context by stating it is 'general sports-fuelling guidance' and specifying what it does not do, which helps set expectations. It does not contradict any annotations, and the added limitations provide clarity beyond the structured metadata.

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 only two sentences, tightly packed with actionable information. It front-loads the core function, then adds usage guidance and exclusions without any waste or repetition. Every sentence earns its place, making it highly concise and well-structured.

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 has four parameters, no output schema, and one sibling, the description provides sufficient context. It explains the high-level output ('bounded carbohydrate target, carry plan and timing guide'), states usage conditions, and clarifies limitations. While it does not detail the output format, the lack of an output schema and the broad guidance nature make this adequate.

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 the input schema fully documents all four parameters. The description adds a slight framing by mentioning 'duration, broad work type and current carbohydrate tolerance' and 'gels, drink, chews or food,' but it does not provide additional detail beyond what the schema already states. This meets the baseline for high schema coverage.

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 opens with a specific action: 'Turn a cycling session duration, broad work type and current carbohydrate tolerance into a bounded carbohydrate target, carry plan and timing guide.' This clearly states the tool's function and resource, and distinguishes it from the sibling 'analyse_event_route' which is route-focused. The second sentence reinforces the purpose by explaining when to use it for fuelling planning.

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?

Explicitly states 'Use this when a rider needs to know how much carbohydrate to carry and how to divide it across their own gels, drink, chews or food.' It also provides clear exclusions: 'does not provide medical nutrition, prescribe hydration or sodium, create a daily meal plan, or use connected athlete data.' This gives both when-to-use and when-not-to-use guidance.

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