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

Annotations only state openWorldHint and idempotentHint; the description adds real value by disclosing the account-wide key requirement and the precondition that the user must already be an account member. It does not mention whether role changes are reversible or notifiable, but it goes meaningfully beyond the 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?

Two tight sentences, front-loading the action and the create-or-update duality, with prerequisites last. The stray '[#5ec6df]' artifact is formatting noise but costs little.

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 3-parameter mutation with no output schema, the description covers the action, prerequisite chain, and auth requirement. An agent has what it needs to call it correctly; only error/failure behavior is left unspecified.

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 coverage is 100% and the role enum is fully documented with per-role meanings in the schema itself, so the description adds nothing beyond 'with a role'. Baseline 3 is appropriate when the schema carries parameter 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 (assign/update role) and resource (account member ↔ workspace), and covers both the create and update cases in one line. Distinguishable from unassign_workspace_member by the outcome, though no sibling is named explicitly.

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?

Gives a clear prerequisite (target must already be an account member; run invite_member first) and an authorization requirement (account-wide key). It does not name when NOT to use it or point at list_account_members/get_role_matrix for discovering valid inputs, so it stops just short of explicit routing.

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