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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description adds genuinely new behavioral context: per-call credit cost, the higher 3-credit PDF price, an output size cap of 1 MiB, inline return, and the meta fields returned. It stops short of disclosing failure modes or sanitisation specifics beyond the word 'sanitised'.

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 purpose and feature list, then output and cost details; every sentence carries information. It is dense to the point of being abbreviated, and the credit cost is stated twice ('1 credit per call' and 'pdf costs 3 credits, html and fragment 1'), a minor redundancy.

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, the description correctly carries the return-value burden, naming the output files, MIME types, size limit, and meta object. Combined with 100% parameter coverage, an agent has everything needed to invoke it correctly.

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 100%, so the baseline is 3, and the description earns above that by tying the format parameter to concrete credit costs and naming the produced files. It does not add anything for css/theme/toc/title beyond what the schema already states.

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 (render) and resource (Markdown) with the exact output set (sanitised HTML page, fragment, or PDF). An agent can distinguish it from siblings like html_to_pdf or html_to_image purely from the description, since the input is Markdown rather than HTML.

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 clear context for choosing among the three output modes (html = page, fragment = content only, pdf = A4 document) and notes relative cost, which helps the agent pick. It does not, however, route the agent away from overlapping siblings such as html_to_pdf when the source is already HTML.

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