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

Annotations already declare destructiveHint=true, idempotentHint=true and openWorldHint=false, so the safety profile is covered structurally. The description adds the required write scope, which is genuine context beyond the annotations, but it does not explain what 'destructive' means here (e.g. whether omitted fields are cleared or preserved) for a tool with 8 optional fields.

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?

Two short sentences with the action front-loaded and zero filler; the scope sentence is short and useful. Slightly under-developed rather than padded, which is the right failure mode.

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?

For a nine-parameter mutation with no output schema, the description plus annotations cover identity, safety and auth, but leave the key ambiguity unresolved: whether this is a full replace or a partial update, and what happens to fields left out. That is the main omission an agent would need.

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% with all nine parameters documented, so the schema already carries the parameter burden and a baseline of 3 applies. The description contributes only the notion that lookup is by ID, adding no meaning about status enum values, date formats, or partial-update semantics.

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 (Update), resource (project milestone) and lookup key (by ID), so the operation is unambiguous. It does not differentiate itself from sibling update tools such as update_project_phase or update_project_task, but the resource noun is specific enough for selection.

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 only guidance is a permission prerequisite ('Requires project_milestones:write scope'). There is no statement of when to prefer this over update_project_phase, bulk_update, or create_project_milestone, and no exclusions for milestones that cannot be modified.

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