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

Annotations already declare the full safety profile (readOnlyHint=false, destructiveHint=true, idempotentHint=true), so the description's remaining job is to add context. It does add the required write scope, which is genuinely useful. It does not explain partial-update semantics, whether omitted fields are preserved, or any side effects of status transitions.

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 zero filler; the operation and its identifier come first and the permission requirement follows. Nothing is repeated or padded.

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 mutation tool with no output schema, the description covers identity and permission but omits update semantics (partial vs full replacement) and error behavior for an unknown ID. Annotations and the fully documented schema cover the rest, leaving this adequate but with visible gaps.

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% across all 7 parameters, including the enum for status and the ISO 8601 formats, so the schema carries the parameter burden. The description's 'by ID' only restates the required field and adds no format or constraint detail 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?

States a specific verb+resource (update an existing project milestone) and the identifying key (by ID), which cleanly separates it from create_project_milestone, get_project_milestone and delete_project_milestone. It stops short of explicitly naming those siblings, so it is clear but not maximally differentiated.

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 contextual guidance is 'Requires project_milestones:write scope', which is an authorization prerequisite rather than when-to-use guidance. There is no statement of when this should be chosen over bulk_update, update_project_phase, or other update siblings.

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