Render an email

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

With no annotations, the description carries the transparency burden. It thoroughly discloses return values, including warnings for non-fatal repairs and previewUrl for live preview, giving a strong behavioral contract. It does not explicitly state side-effect freedom, but the nature of rendering makes this less critical.

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 two sentences: the first delivers the core purpose, the second compactly enumerates return values. Every word earns its place, and it is front-loaded with the most important information.

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?

Since there is no output schema, the description must explain return values, and it does so thoroughly, listing all six output fields and their meanings. Minor gaps like error handling are less critical given the schema covers parameter constraints.

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 schema already documents all parameters. The description adds context about the markdown format (emailmd, frontmatter) but does not elaborate on parameter details beyond the schema, matching the baseline for high schema coverage.

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 clearly states the tool's specific verb and resource: 'Render emailmd markdown into email-safe HTML.' It also lists detailed outputs, distinguishing it from sibling tools lint and read_docs, which serve different purposes.

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 implies this is the rendering step but does not explicitly state when to use it versus alternatives like lint or read_docs, nor does it mention prerequisites or exclusions. Context is clear but guidance on selection is absent.

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