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

The annotation declares destructiveHint true, and the description clarifies the scope: 'The user's ticks, moves and habit history survive; only the template layer changes.' It also discloses a rate limit: 'First 2 revisions per calendar are free.' This adds valuable context beyond annotations.

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 with no fluff. It front-loads the primary action and adds essential caveats in the following sentences.

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 complexity (nested spec object, destructive action, output schema), the description covers the essential context: what is replaced, what survives, and the free limit. The existence of an output schema means return values need not be explained.

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?

With 50% schema coverage, the schema describes spec and reason, but calendar_id and admin_token lack descriptions. The description does not elaborate on parameters; it only refers to 'SprintSpec'. It provides little added meaning beyond the 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 action: 'Replace a calendar's plan with a revised SprintSpec.' It distinguishes from sibling tools like create_calendar (creation vs revision) and validate_spec (validation vs replacement). The mention of 'life happened' scenarios adds context.

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 provides clear context for use: revising an existing plan when life circumstances change (injury, moved exam). It doesn't explicitly mention alternatives or exclusions, but the distinction from creation/validation is implicit.

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