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

Annotations already declare readOnlyHint=false, destructiveHint=false, and idempotentHint=false, so the safety profile is covered. The description adds the role/authorization requirement and the success outcome ('Confirmation of invitation sent'), which are genuine behavioral facts 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?

Front-loads the action in the first sentence, which is good. The Args/Returns block duplicates the schema's parameter listing somewhat, but the Returns line earns its place since there is no output schema.

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 two-parameter mutation with annotations covering the safety profile and no output schema, the description supplies the action, the authorization requirement, both parameter meanings, and an outcome. Only explicit when-to-use guidance 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 description coverage is 0%, so the description must carry the params and it does: 'email: Email address to invite' and 'message: Optional personal message'. It clarifies the message is optional and personal, adding meaning beyond the bare property names, though the detail is shallow.

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 and resource ('Send a family group invitation') with the delivery target ('to an email address'). The action is unambiguously distinct from the family invite siblings (accept/decline/revoke/list_family_invitations), so an agent can route to it 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?

Adds the precondition 'Requires the group owner or admin role', which tells the agent the caller's authority context. However, it never says when to prefer this over related tools (e.g., create_family_group, revoke_family_invitation) or when not to send, so usage is only implied.

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