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

With no annotations, the description must disclose key behaviors, which it does: the output format (full-page PNG), the dual return value (image plus jobId/jobToken), and the cost (USDC 0.02 USD per call). It does not mention side effects like rate limits, but for a read-only capture this is adequate.

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 two sentences with no extraneous words. The main purpose is front-loaded, followed by the return value and cost. Every sentence adds critical information.

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?

The description covers the core purpose, return value, and payment requirement, which are essential for an agent to call the tool correctly. It lacks details on potential errors or timeout behavior, but given the simplicity and schema coverage, it is sufficiently complete.

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 schema documents all parameters. The description adds context about the overall function but does not elaborate on parameter specifics beyond what the schema provides. Baseline 3 is appropriate.

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 action ('Full-page PNG of one URL') with a specific resource and output type. It also distinguishes the tool from get_screenshot by explaining that it returns a jobId/jobToken for later retrieval, making its role in the workflow unambiguous.

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 clear context that this is the first step in capturing and then retrieving via get_screenshot, but does not explicitly state when not to use it or discuss alternatives like start_comparison. The relationship to get_screenshot provides sufficient guidance for common usage.

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