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

Annotations already declare readOnlyHint=true and destructiveHint=false. Description adds value by specifying the exact read outputs (domains, routes, deployed Functions, recent inbound activity), making the scope transparent. No contradictions; could optionally mention auth caveats, but the schema covers api_key semantics.

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, each earning its place: first states the trigger condition, second enumerates the return payload. No filler, front-loaded with the use case. Ideal conciseness.

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?

Given a simple single-parameter tool with an output schema present, the description covers the functional context (inbound readiness check) and return categories. Since an output schema exists, it needn't detail exact fields. Complete and appropriately scoped.

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?

Input schema has 100% description coverage, including detailed guidance on when to include api_key ('Only needed when this connection has no signed-in account...'). The description adds no parameter-level detail, but the schema fully compensates, so baseline 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?

Description clearly states the tool's purpose: 'Use this when the user asks whether inbound email is ready or needs setup.' It also lists what it returns (domains, routes, deployed Functions, recent inbound activity), distinguishing it from siblings like getOutboundStatus by focusing on inbound readiness.

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?

Explicitly gives a when-to-use trigger: 'when the user asks whether inbound email is ready or needs setup.' It does not list exclusions or alternative tools directly, but the specific use case provides clear context relative to siblings. Lacks an explicit 'instead of' alternative, hence not a 5.

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