render_preview

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

Far exceeds the annotations: discloses the ~50 requests/day per-IP rate limit, the HTTP 429 / ok:false failure shape, that tiles requires a self-hosted Playwright host and otherwise degrades to one image, that MICROLINK_API_KEY raises quota, and that published previews expire ~10 minutes after the last publish. This is exactly the behavioral context annotations cannot carry.

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?

A single dense paragraph, front-loaded with the core action and output before engine/rate-limit details. Almost every clause is actionable, though the Microlink doc URL and dual env-var naming add marginal bulk.

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?

There is no output schema, so the description must cover return behavior — and it does: PNG image, multiple band images under tiles, or ok:false on rate limiting. Combined with the expiry caveat and host requirements, an agent has everything needed to call it and interpret results.

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 already 100% for all five params, so the schema carries the parameter burden. The description largely restates the same facts (url precedence, tiles fallback, width semantics) rather than adding new syntax or constraints; the baseline of 3 fits.

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 concrete verb+resource+output: renders a public URL to a PNG screenshot and returns it as an image. It further specifies two targeting modes (page_id vs url) and precedence, which cleanly separates it from every sibling tool (none of which are screenshot tools).

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?

Explains the two input modes and their precedence ('url takes precedence'), the tiles vs single-image choice and its host prerequisite, and full_page defaults. It stops short of explicit when-not-to-use guidance, but the operational context is clear enough for correct selection.

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