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

No annotations are provided, so the description carries the burden of behavioral disclosure. It discloses key constraints (inline styles only, no <style>, no external assets) and the output includes a plaintext alternative. However, it doesn't mention potential limitations (e.g., unsupported Markdown features, handling of images, or whether the plaintext is derived from the HTML or the original Markdown). This is adequate but not rich.

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, well-structured sentence that front-loads the core purpose and then adds key constraints. Every word earns its place; no fluff or repetition.

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?

Given the tool's moderate complexity (Markdown conversion with specific output constraints), the description covers the essential behavior: input (Markdown), output (email-safe HTML with inline styles + plaintext alternative), and constraints (no <style>, no external assets). With no output schema, the description adequately explains what the agent can expect. It could mention edge cases or unsupported features, but for a single-parameter tool, this is largely complete.

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?

The schema has 100% coverage for the single parameter 'markdown' with description 'Markdown source'. The tool description adds context about the transformation (to email-safe HTML) but doesn't add syntax or format details beyond what the schema provides. Baseline 3 is appropriate since the schema already documents the parameter fully.

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 function: 'Render Markdown to email-safe HTML with inline styles only (no <style>, no external assets), plus a plaintext alternative.' It uses a specific verb ('Render') and resource ('Markdown to email-safe HTML'), and distinguishes itself from siblings like 'html_escape' and 'email_clean' by specifying the email-safe, inline-styles constraint and the plaintext alternative.

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 when to use this tool: when you need to convert Markdown to HTML suitable for email, with the explicit constraint of inline styles and no external assets. It doesn't explicitly state when not to use it or name alternative tools, but the context is clear enough for an agent to select it over siblings like 'html_escape' or 'email_clean'.

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