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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds what annotations cannot: that output is dual-format (plain text plus HTML) and includes a per-requirement compliance checklist, which is real value given there is no output schema.

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, front-loaded with the verb and deliverable, and the second sentence earns its place by naming the most common failure mode. No filler or hedging.

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 five all-optional parameters, no output schema, and simple flat fields, the agent has enough to call correctly: it knows the artifact, the two output formats, and the checklist return. Minor gap is guidance on the reply-vs-link-vs-both styles and when each applies, which is left entirely to the schema.

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%, including defaults for tone and style and the note that address is 'Required by CAN-SPAM'. The description's remark that 'a footer with no postal address is the usual failure' reinforces the address parameter but adds no syntax, format, or interaction detail (e.g. that unsubUrl is needed for link/both styles).

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 artifact: 'Build a CAN-SPAM and GDPR compliant opt-out footer in plain text and HTML', and adds that a compliance checklist is included. No sibling tool produces footers (the others are analyze_/check_/plan_ utilities), so the resource is unambiguous.

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?

Usage is implied by the artifact name (you call this when you need an unsubscribe footer), and the closing line steers the agent toward supplying an address. But there is no explicit when-to-use/when-not framing, no mention of prerequisites, and no named alternative for related compliance checks such as check_bulk_sender_requirements.

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