render_template

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

With no annotations provided, the description carries the full burden. It transparently states that the tool renders a template with merge data and returns the subject/html/text, and that it does not send. It does not mention authentication or side effects beyond merging, but is adequate for a non-destructive operation.

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 a single, front-loaded sentence that wastes no words. It efficiently communicates the action, resource, and key behavioral detail (no send).

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?

No output schema exists, so the description must describe the return value. It mentions returning subject/html/text, but does not specify the format (e.g., JSON structure) or whether all fields are always present. This leaves some ambiguity for the agent.

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% and parameter descriptions are clear. The description adds value by explaining that the 'data' parameter is for merge variables, and implies the output includes the rendered fields. This adds context beyond the schema.

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 uses the specific verb 'Render' and resource 'saved template', and clarifies what is returned (subject/html/text) and that it does not send. This clearly distinguishes it from sibling tools like send_email.

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 explicitly states 'no send', indicating this tool is for previewing rather than sending. However, it does not explicitly compare with alternatives like preview_template or send_email, nor provide when-to-use or when-not-to-use guidance beyond the 'no send' flag.

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