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

Beyond the annotations, the description discloses that no email is sent, the invite_url must be shared manually, a general link is invisible in the recipient's inbox until they request access, and that previewing does not constitute a request. These are non-obvious behavioral facts an agent needs before invoking a write.

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?

Purpose is front-loaded in the first clause, followed by compact clauses covering return value and lifecycle caveats. Some sentences are terse to the point of being cryptic ('Pending is not membership'), but nothing is padding.

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?

The tool is a non-destructive write with an output schema, so return values need little explanation; the description nonetheless notes invite_url. With the idempotency contract in the schema, the main remaining gap is undocumented format for space_id/contact_token.

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 only 33% – only idempotency_key is documented in the schema. The description implies contact_token identifies a recipient and space_id is a space you own, but adds no format or constraint detail for these two required-ish parameters, so it only partially compensates.

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+resource ('Invite a contact-token recipient to a private Space') and distinguishes two operating modes: targeted invite vs. a general invitation requiring approval. It does not name sibling tools like space_create_contact_link or space_preview_invitation, so it stops short of full sibling differentiation.

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 clearly states the two conditions under which the tool is used (contact-token recipient vs. general link requiring your approval) and clarifies lifecycle semantics ('Pending is not membership', 'Previewing the link does not request access'). It lacks explicit routing to the alternative tools an agent might pick instead.

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