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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, fully covering the safety profile. The description adds the return content (score, grade, factors) but no additional behavioral traits beyond what is obvious from the name and schema. The description does not contradict 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, zero wasted words. The first sentence defines the tool's output, and the second gives a clear use case. Every sentence 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 simple read-only tool with no parameters and no output schema, the description is nearly complete. It specifies the output and a typical use case. It could be slightly more complete by explicitly stating it returns account-level data, but the current text is sufficient.

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?

There are no parameters, so schema coverage is 100% by default. The description adds value by explaining the tool's output (score range, grade, factors) beyond the empty schema. Baseline for 0 parameters is 4, and the description meets that by providing purpose and return details.

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 retrieves the account deliverability score (0–100) and letter grade (A–F) along with contributing factors. It explicitly names the output format and scope, and the 'Start here' hint differentiates it from more detailed sibling tools like run_deliverability_audit.

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 includes explicit usage guidance: 'Start here when asked why emails are landing in spam.' This clearly indicates the primary use case. However, it does not explicitly mention when not to use this tool or name alternatives, leaving room for slight ambiguity.

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