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

Annotations establish it's a read-only, non-destructive operation, so the bar is lower. The description still adds valuable billing and caching context: 'Creating the link is free. Opening it renders the page and uses one capture from this account (a recent cached copy is served free).' This tells the agent that opening the link consumes credits, not just creating it. Missing explicit mention of auth requirements beyond 'no API key needed.'

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?

Three sentences, front-loaded with what the link is and does. Efficient, but the billing/caching detail could be slightly tighter.

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 tool with a rich 15-param schema (100% coverage), the description covers the key non-schema concerns: sharing purpose, cost model, and link expiration. No output schema exists, but for a link-creation tool the output (the signed URL) is self-evident. Adequate.

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 100%, so the input schema already documents all 15 parameters thoroughly. The description only adds the expires_in default behavior ('default: 1 day'), which the schema also states. Baseline 3 is correct when schema does the heavy lifting.

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+resource ('Create a signed link that renders a screenshot') and distinguishes from siblings by noting it's a shareable link requiring no API key, unlike take_screenshot which presumably returns an image directly.

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?

Clear context for when to use: 'for emails, documents or sharing with others.' Does not explicitly exclude use cases or name alternatives, but the sharing-with-others framing is sufficiently differentiated.

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