What VaEmail can do

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

Annotations already cover readOnlyHint, idempotentHint, and destructiveHint. The description adds the behavioral fact 'No API key needed', which is not present in annotations and is valuable for an agent deciding whether to invoke this tool without authentication. No contradiction with annotations.

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, front-loaded with the returned content, followed by the auth requirement and usage guidance. No filler; every word earns its place.

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 capabilities-discovery tool with no parameters and no output schema, the description fully covers what the agent needs: what is returned, the lack of auth, and when to call it. Nothing missing for correct invocation.

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 clarify. Baseline for 0-parameter tools is 4, and the description's focus on return content 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 states a clear verb ('Return') and a specific resource ('what VaEmail supports'), enumerating the content (interfaces, capabilities, limits, scopes, region). It explicitly frames itself as the entry-point capability tool, distinguishing it from sibling tools that perform diagnostics, listings, or sending.

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 explicitly says 'Call this first when deciding whether VaEmail fits a need', which gives a clear when-to-use directive and implies ordering relative to siblings. It does not explicitly name alternatives, but the 'first' directive plus the sibling list makes the intended usage unambiguous.

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