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

Goes well past the annotations by disclosing a hard validation gate: templates with raw/unknown tags, a tag after a greeting, http images, missing alt text, placeholder links, or over 102 KB are refused with remediation hints. It also documents the merge-tag dialect ([[key]] works, {{…}} is not substituted), which is exactly the kind of silent-failure trap an agent would otherwise fall into.

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?

Front-loaded with the action and the sibling fork before the validation detail, and every clause carries information. The final sentence is a long comma-heavy list, which slightly hurts scannability but nothing is 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 5-parameter write tool with no output schema, the description covers creation semantics, the alternative tool, merge-tag usage, and failure modes thoroughly. Minor gaps: no mention of dry_run as the safe way to preview validation failures, and no note on what happens to category_id/plain_text defaults.

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 coverage is 100%, so the baseline is 3; the description nonetheless adds real meaning for the critical `html` parameter by specifying the merge-tag syntax and the content rules that cause rejection. It says nothing about dry_run, plain_text, or category_id, which remain schema-only.

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 ('Create a new email template') plus the input mode ('from HTML the user pasted or supplied'), and explicitly contrasts with the sibling create_dnd_email_template. An agent can distinguish this from create_dnd_email_template and clone_template without opening a schema.

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 an explicit routing rule: for a designed email use create_dnd_email_template instead so it opens in the drag-and-drop editor. It also points to list_custom_fields as the source of merge-tag keys, so the agent knows the prerequisite call sequence.

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