render_preview

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

Annotations already declare readOnlyHint and openWorldHint, so the tool is read-safe and open-world. The description adds critical behavioral details: the underlying engine (Microlink), rate limiting (HTTP 429 with fallback to skip), preview expiration, and the need for a self-hosted Playwright for tiles. No contradictions.

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 comprehensive but somewhat verbose. It is well-structured with clear sections (AGENT-FIRST, ENGINE, NOTE, TALL PAGES) and front-loads the core purpose. However, some details could be more concise without losing utility.

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?

While the description covers many aspects, it does not fully specify the normal success response format (e.g., what fields are returned, how the image is encoded). It mentions an 'ok' field for errors but not the success structure. Given no output schema, this leaves a gap in understanding what the tool returns.

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 covers all 5 parameters with descriptions, but the description adds practical guidance beyond the schema: for width (recommended values), for tiles (requires Playwright, fallback), and for url/page_id precedence. This extra context improves usability significantly.

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 purpose: render a public URL to a PNG for visual comparison, specifically for the fidelity-check step in a clone loop. It distinguishes between using a page_id or a URL, and mentions it's an alternative to the agent's own screenshot capability, making it unique among siblings.

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?

It explicitly tells when to use (for visual fidelity check) and when not to (if agent has screenshot capability). It provides limitations: rate limit (~50/day), preview expiration (~10 min), and fallback behavior for tiles. It also suggests alternatives (agent's own tool) and best practices (call promptly after create/publish).

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