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

Annotations already declare readOnlyHint=true, destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral information: resolving a token confers no membership or private-message access, which is a security-relevant guarantee an agent would otherwise have to guess at. It does not discuss token expiry or error states, keeping it below a 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?

Two short sentences, zero filler, with the security clarification deliberately placed after the primary purpose. Nothing could be trimmed without losing information.

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?

An output schema exists, so return values need not be explained, and annotations cover the read-only safety profile. For a single-parameter lookup the description supplies purpose, usage moment, and access-scope caveat; only error/expiry behavior for invalid tokens is left unaddressed.

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 is one required parameter at 0% schema description coverage; only the regex pattern is documented structurally. The description does convey that contact_token identifies a person ('who a contact token belongs to'), adding real semantic meaning, but says nothing about where the token comes from or how to handle malformed values.

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 ('Check') and resource ('contact token') plus the outcome ('who it belongs to'), which distinguishes it from space_create_contact_link (minting a token) and space_invite_member (granting membership). It stops short of naming those siblings explicitly, but the intent is unambiguous.

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 clause 'before inviting them' implies a pre-invite lookup workflow, which is useful context. However, there is no explicit when-not, no named alternative such as space_preview_invitation or space_get_actor, and no statement about what to do if the token is invalid or expired.

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