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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds real behavioral context beyond that by clarifying the capability boundary — no message submission is possible and visitors must use their own email app or the site form — which prevents an agent from misusing the result.

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, front-loaded with the core purpose, with no filler. The capability caveat is compact and earns its place, though it could have been folded more tightly into the first sentence.

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 an output schema documenting the returned fields and annotations covering safety, the description only needs to convey purpose and constraints, which it does. The one gap is not naming which contact channel (email) is returned, but the output schema fills that.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The schema is trivially complete at 100% coverage.

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?

"Returns canonical contact information" gives a verb and a resource, but the resource is vaguer than the tool name implies (email vs. generic "contact information"). It never distinguishes this from sibling lookups like get_social_profiles or get_professional_profile, so an agent gets only a rough sense of what comes back.

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 second sentence establishes a clear when-not-to-use boundary: this tool cannot send messages, so an agent should not invoke it to contact anyone. However, there is no positive guidance on when to pick this over the many sibling context-fetching tools, leaving usage only implied.

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