contact

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

Annotations already declare readOnlyHint=true, so 'Changes nothing' is reinforcement rather than new information, but the description adds genuinely useful behavioral context: the data is drawn only from recent Inbox/Sent mail of every mailbox the app may use, and unmatched addresses return an error. It does not cover permissions or latency, but for a read tool the disclosure is strong.

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 sentences, front-loaded with what is returned, then the alternative, then the safety/scope caveat. Every sentence carries decision-relevant information; nothing is filler.

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 the return shape need not be re-explained. Combined with the usage routing, the exact-match requirement, and the data-source/error caveat, an agent has everything needed to call this correctly.

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 100% but the schema only says 'The person's email address.' The description adds the exact-match constraint that the schema omits, which materially changes how an agent must supply the value (no partial or fuzzy addresses).

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?

Specific verb (Show) plus resource (one person) with the exact key (exact email address) and the payload it returns (name, sent/received counts, last date). It is clearly distinguishable from the sibling 'contacts' lookup, which it explicitly contrasts.

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?

States the routing rule outright: 'To find someone by name or part of an address, use contacts first.' It also gives the negative condition — an address outside the indexed mailboxes yields an error — so the agent knows when this tool will fail.

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