sender_history

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is known. The description adds valuable context beyond that: it specifies that this is a local call (no provider call), that results may be empty if the index isn't built, and it outlines the return structure. This goes beyond what annotations provide and helps the agent set expectations. No contradiction.

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?

The description is two sentences plus a short note. It front-loads the core purpose, then adds usage context and the key caveat about local-only and empty results. Every sentence earns its place with no redundancy or fluff.

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?

For a read-only tool with two well-documented parameters and no output schema, the description covers the essential points: what data it returns (profile and context), when it's useful, the local-only nature, and when it returns empty. It could be slightly more explicit about the exact fields, but the example placeholders give sufficient orientation. Overall complete for an agent to call it 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 description coverage is 100%, so both parameters (email and account_id) are already documented in the schema. The description doesn't add much about parameter semantics beyond what the schema says, but it implicitly connects the email parameter to the sender being queried. Since the schema does the heavy lifting, a baseline of 3 is appropriate.

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 clearly states the tool's purpose: it retrieves what GigaMail's local index knows about a sender, including profile and context. It distinguishes itself from siblings by focusing on sender-level metadata rather than message content or account info, so an agent can differentiate it from list_messages or get_identity.

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 description gives clear context for when to use it ('useful to reply in the right register and avoid repeating yourself') and notes that it is local-only and empty when the index hasn't been built. It doesn't explicitly name alternatives or state when not to use it, but the local-only and empty conditions effectively guide usage. Lacks explicit exclusions, but the guidance is strong.

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