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

With no annotations, the description carries the full burden. It does add genuinely useful non-schema context: the $0.005 per-call price and 3 free calls/day rate limit. However it omits the return format (URL vs base64 image), whether auth is required beyond the free tier, and any timeout/error behavior for a 23-param network-driven tool.

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?

Two compact sentences, front-loaded with the core capability followed by the cost model. No filler or repetition, though the pricing sentence could arguably be deferred to a general note.

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?

For a 23-parameter tool with no annotations and no output schema, the description is thin: it never states what the tool returns (image bytes, a stored-file URL, etc.) and leaves most behavioral and parameter surface undocumented. This is well short of what an agent needs to invoke it confidently.

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 only 35% across 23 params, so the description must compensate. It partially does by naming fullPage, clip, omitBackground, and the quality 0-100 jpeg/webp constraint, but the large majority of parameters (cookies, authenticate, waitForSelector, deliver, bestAttempt, etc.) get no explanation anywhere.

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 states a specific verb and resource ('Capture a PNG, JPEG or WebP screenshot') and names the underlying mechanism (Puppeteer's page.screenshot()). It is clearly distinguishable from pdf/markdown/links siblings, though it does not explicitly contrast with the closest sibling, snapshot.

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 gives no when-to-use or when-not-to-use guidance and names no alternative among the siblings (links, markdown, pdf, snapshot). The only routing hint (url vs html) lives in the schema, not the description.

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