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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so safety is covered. The description adds valuable behavior: it returns weekly evolution of VO₂max, running economy, LT₂, and predicted finish, plus cites the source module. This goes beyond annotations without contradicting them.

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 two concise sentences: the first states the core function and inputs, the second lists outputs and source. No wasted words, front-loaded with action, and every element earns its place.

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 output schema present, the description doesn't need to detail return structure, but it still summarizes outputs. It adequately covers the tool's purpose and main inputs. However, it doesn't mention how baseWeeks/buildWeeks interact or that totalWeeks defaults to 16, though those are in the schema. Given the complexity and rich schema, this is sufficient but not exhaustive.

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 baseline is 3. The description mentions weekly volume and starting marathon time, but these are already fully described in the schema. It doesn't add extra semantic meaning to parameters beyond what's provided, so it doesn't exceed the baseline.

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 uses a specific verb ('Forecast') and clearly states the resource: race-time progression across pyramidal, polarized, and threshold models. It distinguishes itself from siblings like predict_race_time (single prediction) and generate_training_plan (plan creation) by focusing on model comparison.

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 when to use the tool: when comparing periodization models for a given volume and starting time. It doesn't explicitly state exclusions or name alternatives, but the context is clear enough from the content and sibling tool names. The lack of explicit 'use this instead of X' prevents a 5.

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