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

Beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=true), the description discloses invite lifetime (7 days), resend semantics, authorization and plan requirements, and the idempotency contract (same key returns the first answer and does not act again). These are the exact behavioral details an agent needs before invoking a mutating, email-sending tool.

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?

Five short sentences, each carrying distinct information (action, duration, resend rule, prerequisites, idempotency), with the core action front-loaded. No filler or 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?

An output schema exists, so return values need not be described; the description covers everything else an agent must know (permissions, plan, invite expiry, retry safety). Nothing material 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 coverage is 50%, and the one documented parameter (idempotency_key) is already explained by the schema text, which the description largely echoes. The description never states explicitly that `email` is the invitee address, so it adds only marginal meaning beyond structured fields; baseline 3 is appropriate.

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 names a specific verb and resource ('Sends an email invitation to join the workspace as a member'), which is unambiguous and clearly distinct from read-oriented siblings like list_members or get_workspace. An agent can identify the operation without opening the schema.

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 concrete preconditions ('Admin only, on a paid plan') and clarifying conditions for repeat use ('Inviting the same address again sends a fresh email'), which is strong context. It stops short of naming alternatives such as create_share_link for granting access without an email invite, so it is not a full when/when-not routing statement.

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