get_fitness

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 the important computational nuance that form is computed as CTL − ATL because intervals.icu exposes no form field, and states the default date range. It doesn't cover permissions or error behavior, but for a read-only trend tool this is reasonable.

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 three concise sentences that front-load the purpose, explain the one non-obvious computation, and then provide the default and interpretive guidance. Every sentence earns its place with no wasted words.

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 simplicity, an output schema exists, and the description covers the essential behavioral aspects (what metrics, how form is derived, default range, and how to interpret the trend), it is complete. There is no significant gap for an agent to misuse the tool.

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 schema already explains the start_date and end_date parameters thoroughly with defaults. The description redundantly mentions the 28-day default but adds no new parameter-level details beyond the schema, so the baseline of 3 is appropriate.

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 shows the fitness trend with specific metrics (CTL, ATL, form/TSB) on a per-day basis. This specific verb+resource combination distinguishes it from sibling tools like get_power_curve or get_activity.

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?

It provides clear context on when to use it (e.g., defaults to last 28 days) and interprets the trend's meaning (peaking vs. digging a hole). It doesn't explicitly name alternatives or exclusions, so it stops short of a 5, but the usage context is solid.

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