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

Annotations already declare idempotentHint=true, destructiveHint=false, and readOnlyHint=false, so the safety profile is covered. The description adds real context beyond that: the server verifies the caller is the invitee via email/tenant match, and the invitation must still be pending. It stops short of saying what a successful decline returns or what error surfaces on a mismatch, hence a 4 rather than 5.

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?

Three short clauses, front-loaded with the action and its precondition, with the alternative routing placed last where it belongs. No sentence is redundant 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 single-param mutation with no output schema, the description supplies the operation semantics, the authorization check, and the sibling alternative. The only minor gap is the absence of any statement about failure modes (e.g., non-pending invitation, non-invitee caller), which annotations do not cover.

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?

With one parameter and 100% schema description coverage, the schema already fully documents grant_id as the UUID of the invitation. The description adds no syntax, format, or sourcing detail beyond what the schema provides, so the 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?

The description names a specific verb (Decline), the exact resource (a pending status=invited namespace invitation), and the actor role (as the grantee). It also distinguishes itself from the sibling revoke_grant by naming it as the grantor-side alternative, so an agent can separate the two without opening either 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 states the precondition for use (the invitation must be pending, status=invited), restricts who may call it (the grantee), and explicitly routes grantors to revoke_grant instead. Both the 'when' and the 'when-not'/alternative are given, leaving little to inference.

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