site.context

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

The description adds meaningful behavior beyond the annotations: it discloses auto-open semantics, that existing tabs are never replaced, and that credentials/page bodies are not returned. These are substantive traits that the annotations (readOnlyHint=false, openWorldHint=true, destructiveHint=false) do not convey. It could mention rate limits or side effects more explicitly, but the coverage is strong.

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 tightly written sentences, each adding distinct information: what the tool does, how openIfMissing changes behavior, and safety boundaries. Zero waste, front-loaded with the core purpose.

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 3-param, no-output-schema tool with annotations covering safety traits, the description is complete enough: it covers the core action, the optional open behavior, and the non-return of sensitive data. It omits explicit notes on return shape or error conditions, but nothing critical is missing for correct invocation.

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 0% for all 3 parameters, so the description must compensate. It explains the behavior of openIfMissing and the roles of site/url ('with a site or supported URL'), adding meaningful semantics beyond the raw schema. Some ambiguity remains (e.g., what 'supported URL' means), but it is effective.

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 and resource ('List browser targets') and explains what the targetIds are (opaque). It clarifies the resource but does not distinguish itself from site.discover or site.execute, so it falls short of the 5 that requires sibling differentiation.

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 a clear behavioral rule ('set openIfMissing=false for a pure lookup') that informs usage, and it states scope ('with a site or supported URL'). It lacks explicit when-to-use-this-vs-alternatives guidance against the sibling tools, but the openIfMissing toggle is a concrete usage condition.

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