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

Annotations already flag readOnly=false and destructive=true, so the description earns credit for adding real signal: partial-field semantics, that built-in starters are editable but not deletable (softening the destructive hint), and that the change affects future sends without triggering one. It still says nothing about permissions, whether a rewrite is reversible, or what the response contains.

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, front-loaded with the mutation scope, then the built-in exception, then the non-send clarification. No filler and no repetition of the title or annotations.

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 6-parameter mutation tool with no output schema, the description covers the semantics of the optional fields well but omits the required templateId and the project override, and does not describe the return value or confirmation. Adequate but with a clear gap on the one field every call must supply.

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 only 17% (just the `project` field), so the description does real work by naming four of the six fields and explaining the only-fields-sent behavior. However, the required `templateId` and the `project` scoping parameter are not mentioned at all, leaving gaps the schema doesn't fill either.

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 and enumerates the mutable fields (name, category, subject, body), which instantly separates it from create_template and update_widget-style siblings. The added note that built-in starters can be rewritten is a concrete scope statement, not a restatement of the title.

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?

"only the fields sent" makes clear this is a partial-update tool, so an agent knows it need not read-then-write the full object. It also implicitly distinguishes update from create and from send-time behavior ("sends nothing"), but it never names list_templates as the prerequisite for obtaining a templateId, nor states any when-not condition.

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