List supported mail providers

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

Annotations already mark this as read-only and open-world, and the description adds useful behavioral context: it lists providers, explains where passwords come from, mentions the IMAP_HOST mechanism for generic providers, and clarifies that OAuth-backed providers are preferred when available. This goes beyond the annotations without contradicting them.

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 compact and front-loaded with the core purpose, then adds only relevant setup context. Each sentence contributes either to what the tool lists, when to use it, or how provider selection works. No filler or redundancy.

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 no-argument discovery tool with an output schema, the description is complete enough. It tells the agent why to call it, what it will find, how passwords are obtained, and how generic vs. OAuth providers relate. The output schema covers the return structure, so no additional return-value detail is needed.

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 has zero parameters, so the baseline is 4. The description appropriately explains what the tool returns conceptually, and there are no parameter details needed beyond the empty 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?

The description opens with a clear verb and resource: 'List the mail providers this server knows, and where to get a password.' It also sets the tool in a setup context, distinguishing it from the sibling IMAP operations like imap_health and imap_search_messages, which address different concerns.

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 explicitly says 'Start here when setting up,' which gives clear when-to-use guidance. It also explains the relationship between generic IMAP providers and preferred OAuth connectors, although it does not name a direct alternative tool because none exists for this purpose.

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