Resolve fmsg address

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

Description discloses the exact resolution logic: literal addresses pass through, directory lookup is attempted, then a default-domain fallback, and failure when nothing matches. This goes beyond annotations by describing order and failure conditions. It also reinforces readOnlyHint with 'without sending anything'.

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 sentences carry substantial meaning with no filler. The main action is front-loaded and the failure behavior is included as part of the same compact explanation.

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 single-parameter resolver, the description covers every outcome: literal, directory hit, default domain, and failure, plus side-effect safety. An output schema exists to document the return shape, so the description does not need to repeat it.

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?

Although the schema already describes the parameter (100% coverage), the description deepens meaning by explaining how the value is interpreted: a literal @user@domain is returned as-is, otherwise directory/default domain logic applies. This tells the agent exactly what input forms are acceptable and what behavior each triggers.

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 uses the specific verb 'Resolve' and identifies the exact resource: a short name converted to a full fmsg address. It also states the side-effect-free nature ('without sending anything'), clearly distinguishing it from messaging tools. The three-step resolution order removes ambiguity about what the tool does.

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?

It implies when to use the tool: anytime you need a canonical address before addressing recipients, and explicitly explains failure behavior. It does not name sibling alternatives, but none of the listed siblings perform address resolution, so the context is clear. Could add an explicit 'use before add_recipients/send_message' but that is inferable.

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