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

The annotations already declare readOnlyHint=true and openWorldHint=true, so safety and external-network behavior are covered. The description adds useful scope by naming the protocols inspected, but it does not disclose return format, rate limits, or operational behavior beyond what the annotations and title provide.

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 a single, front-loaded sentence that efficiently names the action and enumerates the standards. Every clause contributes specific scope without filler.

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 read-only, single-parameter inspection tool with no output schema, the description gives enough context to invoke it correctly and understand its scope. It could be more complete by hinting at the nature of the returned report or when to prefer it over related DNS tools, but the core invocation needs are met.

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 is one parameter ('domain') and schema description coverage is 100%, so the schema already documents it fully. The description adds no syntax, format, or constraint details beyond the schema, making the baseline 3 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 uses a specific verb ('Inspect') and resource ('domain email security and deliverability standards'), then enumerates the exact protocols checked (DMARC, BIMI, MTA-STS, SMTP TLS-RPT, SPF, MX). This distinguishes it from sibling tools like trace_dns_delegation and diagnose_cors_policy, which cover different domains.

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 implies the tool is used for email-security and deliverability checks on a domain, but it does not explicitly state when to choose this over alternatives or any prerequisites/exclusions. Usage is inferable from the listed standards, matching the 'implied usage' level.

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