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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the agent knows this is a safe read-only operation. The description adds valuable behavioral context: it returns a copyable record with placement instructions, uses no credit, and requires a Pro plan. This goes beyond what annotations provide, covering return format and constraints. 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?

The description is compact: one sentence for purpose, one for output, and one line for caveats (no credit, Pro plan). It's front-loaded with the core purpose, then return details, then constraints. No redundant wording; 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 tool with 14 parameters and no output schema, the description sufficiently explains what it does, what it returns, and important constraints (credit, plan). Parameter details are fully delegated to the schema, which is acceptable. The only gap is not clarifying parameter dependencies (e.g., BIMI requires logoUrl), but that's beyond the description's role.

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 schema describes all 14 parameters (100% coverage), including enums and descriptions, so the schema does the heavy lifting. The description itself adds no parameter-specific semantics beyond naming the four record types, which maps to the 'type' parameter. Per rubric, baseline 3 applies when schema coverage is high; no additional value from the description.

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 names a specific verb ('Create') and resource ('email-authentication DNS record'), explicitly enumerates the four record types (SPF, DMARC, BIMI, MTA-STS), and explains the output. This clearly distinguishes it from sibling verification/checking tools, which focus on analysis rather than generation.

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 states a clear context: 'so its email is trusted and harder to spoof', and lists the record types it supports. It doesn't explicitly name alternatives or exclusion criteria, but the sibling list (all verification/checking tools) makes it obvious this tool is for generating DNS records, not verifying. Clear context without explicit exclusions warrants a 4.

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