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

Annotations only declare idempotentHint and destructiveHint, leaving the interaction model unstated. The description fills that gap with the non-obvious facts: no email is sent, an acceptance link is returned, and messaging stays disabled until the recipient accepts — exactly the context an agent needs before calling.

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?

Three short clauses, front-loaded with the action, then the scope exclusion, then the return/side-effect behavior. No filler and nothing redundant with annotations.

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?

With no output schema, the description correctly explains what is returned (an acceptance link) and the side-effect gating. Minor gaps remain: behavior when the contact already exists and any permission prerequisites are 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?

Schema coverage is 0% but the single parameter is mechanically self-describing (format: email with a full pattern). The description adds semantic value by noting the email belongs to a 'new contact', which is not expressed in the schema.

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 (prepare), resource (private direct chat invitation), and scope constraint (by email, without creating a shared project). This cleanly distinguishes it from invite_to_shared_project and open_direct_chat in the sibling list.

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 phrase 'without creating a shared project' implicitly tells the agent this is the non-shared-project path, which is the key selection criterion versus invite_to_shared_project. It does not explicitly name the alternatives or state exclusions, so it stops short of a 5.

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