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

The annotations already declare a non-readonly, non-idempotent, non-destructive, closed-world mutation. The description adds meaningful behavioral context about approvals: MCP approval requirements are administrator-configurable, while business workflow approvals always apply; it also states the account/permission boundary. It does not cover permission prerequisites or duplicate-member behavior.

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 sentences, front-loaded with the core action and followed by boundary and approval context. Every sentence adds useful information without repetition.

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 two-parameter mutation with annotations and an output schema, it covers purpose, precondition, boundary, and approval context well. Remaining gaps such as role defaults and duplicate-member handling are modest but keep it from a 5.

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 0%, so the description must carry parameter meaning, and it does identify the core semantics: projectId is the project, data.userId is an existing organization user, and data.role is optional. It does not document UUID formats or role constraints, but the schema types still convey those.

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 states a specific verb and resource: assign an existing organization user to a project, with an optional project role. It also distinguishes the action from account creation and organization permission changes, which helps separate it from invite/user-management siblings.

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?

It gives clear usage context by requiring an existing organization user and explicitly excluding account creation and organization permission changes. It does not name the sibling tools to use for site team membership or for inviting new users, so it stops short of full alternative routing.

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