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

Goes well past the annotations by disclosing the required auth scope, the owner-level permission, and — most valuably — that emails are masked to email_domain and the full address must never be claimed. The opening "Read-only; changes nothing" only restates readOnlyHint/destructiveHint, but the rest is substantive and hard to get elsewhere.

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?

A single front-loaded sentence plus one bracketed caveat; the safety claim, the scope, the returned fields, and the masking warning are all ordered before any padding. Nothing wasted.

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 one-parameter read with no output schema, the description supplies returned fields, auth requirements, the caller's permission level, and the PII-masking limitation — everything needed to call it and to report results honestly.

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?

One parameter at 100% schema description coverage, and the schema already explains it is the id from list_sites. The description's "this site" and "the site's owner" add no syntax or format detail beyond that, so baseline 3 applies.

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 the resource (the site's open invitations) with a scope qualifier ("still open") and enumerates what comes back — id, role, expiry. That is enough to distinguish it from site_members or a general invite listing 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?

Names the downstream consumer explicitly ("the id revoke_invite needs") and states the permission prerequisite (key scope sites:read, site owner). No explicit when-not or named in-list sibling alternative, which keeps it below a 5.

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