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

Annotations already establish readOnlyHint, idempotentHint, and non-destructive behavior. The description adds useful context by specifying 'pending' and clarifying that both received and sent invitations are returned, but it does not go beyond that into other behavioral details.

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 brief, front-loaded with the main purpose, and then clarifies the return content. Every sentence contributes meaning without redundancy.

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 zero-parameter, read-only listing tool with strong annotations, the description is nearly complete: it states what is listed and what will be returned. A small gap is that it does not describe the expected shape or fields of an invitation, but this is not critical for selecting or invoking the tool.

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?

There are zero parameters, so the empty schema fully covers invocation needs. The description doesn't need to explain parameters, and the no-input behavior is clear from the schema context.

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 uses a specific verb and resource: 'List pending family invitations', and further scopes it to 'sent to you or by you'. This clearly distinguishes it from action-oriented siblings like accept, decline, send, and revoke invitation tools.

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?

The description makes the tool's basic use context obvious: it lists pending invitations in both directions. However, it does not explicitly state when to choose this over related tools such as accept_family_invitation, decline_family_invitation, or send_family_invitation.

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