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

Annotations already cover readOnly/idempotent/non-destructive, and the description adds two genuinely useful facts beyond them: the return shape (record name, value, type) and the explicit boundary that mailX does not publish the record. It stops short of describing validation behavior or record formatting details.

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?

Three short sentences, zero filler, with the trigger condition front-loaded and the output/limitation facts following. 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?

With no output schema, the description usefully names the returned fields and clarifies that publishing is out of scope, and annotations cover the safety profile. It leaves the practical question of how the returned record is applied somewhat open, hence not a 5.

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?

Schema description coverage is 100%, with each of the three required parameters documented including the enum meanings for dmarc_policy and examples for domain_name and email. The description adds no parameter-level detail, so the 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?

States a specific verb and resource ('generate a DMARC record') and distinguishes itself from the check-style tools by framing the trigger as 'the user needs a DMARC record'. It never names the obvious sibling (dmarc_check) or the analogous spf_generate, so the differentiation is implied rather than stated.

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?

Gives a use context ('when the user needs a DMARC record') but no when-not-to-use and no alternative named. An agent must infer that dmarc_check is for inspecting existing records while this one creates a new one.

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