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

Annotations already establish readOnlyHint=false and destructiveHint=false, so the safety profile is covered. The description adds real behavioral context by revealing that the general-link branch only creates an approval request rather than immediate membership, but says nothing about failure cases, idempotency, or what membership state results.

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?

Two sentences, no filler, with the dual-mode behavior stated first and the parameter constraint stated last as the operative rule. Every sentence carries information an agent cannot get from the 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?

Output schema and annotations cover return values and safety, and the description covers the mutual-exclusivity rule. Still missing: what happens if neither parameter is supplied (required is 0) and which identifier corresponds to the direct-invitation versus general-link path, which is exactly the ambiguity an agent would hit.

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 compensate. It does add the critical 'exactly one of' exclusivity constraint that the schema does not encode (both params are optional with no oneOf), but it does not explain which identifier belongs to which flow or why the patterns differ (iv_ vs i_).

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?

Uses a concrete verb+resource (accept an invitation) and explicitly splits the behavior into two modes: accepting a direct invitation versus requesting owner approval for a general link. This distinguishes it functionally from space_approve_invitation and space_preview_invitation, though it never names those siblings.

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 two branches ('addressed to you' vs. 'general link') give a clear condition for choosing each flow, and the final sentence gives the argument-selection rule. It stops short of routing to alternatives such as space_approve_invitation or space_list_invitations.

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