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

Goes well beyond the annotations by disclosing a derived side effect (completed=true stamps completedAt=now(); flipping back clears it) and the exact authorization requirement (milestone.create permission, MEMBER and above under the default matrix, or org admin). These are non-obvious behaviors that annotations alone (destructiveHint/idempotentHint) do not convey, and nothing here contradicts 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?

Three tight sentences, front-loaded with the field list and followed by the two highest-value details (side effect, permission). Every clause carries information an agent needs.

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 no output schema, the description still covers the mutable surface, the notable side effect, and the authorization gate for a destructive-capable write. Nothing essential for correct invocation is missing.

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 only 25% (only dueDate is annotated as ISO date), so the description must compensate — and it does for 'completed' by explaining its toggle semantics and derived completedAt behavior. It adds no format detail for title or milestoneId, which remain self-evident but unannotated.

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?

States a specific verb and resource ('Update milestone fields') and enumerates exactly which fields are mutable (title, dueDate, completed). An agent can immediately distinguish it from create_milestone, get_milestone, list_milestones, and propose_milestone_completion.

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 field list and permission note imply the usage context (editing an existing milestone), but the description never states when to use this versus alternatives like propose_milestone_completion or update_task, nor any when-not conditions. Usage is inferable rather than explicit.

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