session_verdict

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

The readOnlyHint annotation is reinforced and extended with valuable behavioral detail: it is pure code over existing signals, takes no screenshots, runs no page evals, executes in single-digit milliseconds, and never bypasses protections. The description also discloses that challenge responses carry a handoff instruction for human resolution, adding context beyond the annotation.

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 front-loaded with the core purpose ('One call answers where did this session land') and then delivers a dense but relevant enumeration of verdicts, facts, and behavior. It is long but every clause earns its place; a list format would improve scannability, but the content is not wasteful.

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?

With no output schema, the description carries the burden of explaining return semantics, and it does so thoroughly: all verdict categories, the facts sheet contents, handling of non-2xx documents, and the safety/performance profile. For a one-parameter classification tool, an agent has enough context to call it correctly and interpret the result.

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 for the single parameter is 100%, so the schema already documents session_id. The description does not add any additional meaning about the parameter itself, which matches the baseline of 3 when structured 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?

The description clearly states the tool's job: classify where a session landed, and enumerates the possible verdicts (challenge, captcha, login, empty, landed, unknown) with concrete meanings. It distinguishes itself from action tools by saying it 'observes, never bypasses' and uses 'no screenshots, no page evals,' but it does not explicitly differentiate itself from similar observation tools like session_state or session_network.

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 for when to call it: after a session action, to answer 'where did this session land' and to branch on the resulting verdict/facts, including handling non-2xx documents via facts.doc_status. It does not explicitly name alternative tools or state when not to use it, but the intended use case is strongly implied.

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