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

Goes well beyond the readOnly/idempotent annotations: it discloses that html_to_markdown drops scripts, styles, forms and media and returns the page title, and that markdown_to_html sanitizes raw HTML and unsafe-scheme links. It also states the no-auth requirement, which the annotations do not cover, and since there is no output schema this return-value detail is essential.

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 core conversion statement, then two direction-specific sentences, then the auth note. Sentences are dense with useful detail rather than padding, though the closing 'No API key, no account and no sign up' is slightly redundant with the rest of the benefit framing.

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?

With no output schema and only two parameters, the description carries adequate load: it explains both directions' outputs, sanitization, and auth. The main gaps are the max-length limit on input and any error/edge-case behavior (e.g., malformed HTML), which an agent might need.

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 baseline would be 3, but the description adds real meaning to the 'direction' enum by explaining the output shape and sanitization behavior of each branch (CommonMark with GFM tables, strikethrough, task lists). The 250,000-character 'data' cap is never mentioned, so size constraints 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 ('Convert HTML to Markdown, or Markdown to HTML') and immediately names both direction values, so an agent knows exactly which transformation it gets. It does not explicitly distinguish itself from the nearby sibling html_to_pdf, which is the one conversion tool an agent might confuse it with.

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 concrete usage contexts: html_to_markdown is for making a fetched page read with fewer tokens, and markdown_to_html is for producing HTML that can go into a page as-is. There are no explicit when-not-to-use conditions or named alternatives, but the intended scenarios are clear.

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