end_session

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

With no annotations, the description carries the full burden and does well: it discloses that sites are signed out and the browser profile is destroyed, and that the vault performs this automatically if the agent stops or is revoked. It does not state whether the destroyed profile means lost cookies/state or whether the operation is recoverable, leaving a modest gap.

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 short sentences, front-loaded with the action and its effects before the operational instruction. The parenthetical about automatic invocation earns its place by explaining fallback behavior, though the phrasing is slightly loose.

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 zero-parameter, zero-annotation tool with an output schema present, the description covers purpose, trigger, side effects, and automatic fallback. Nothing an agent needs in order to invoke it correctly is missing.

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?

Zero parameters, so the schema has nothing to document and there is no parameter semantics to explain. Baseline 4 applies per the rubric for parameterless tools.

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 (end) and resource (the owner's session), and goes further by describing the mechanism: signs out of sites, then destroys the browser profile. This clearly distinguishes it from every sibling, which are page-interaction tools (navigate, click, read_page).

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?

"Always call this when you are finished with the web" gives an explicit trigger condition, which is stronger than most tools. It lacks an explicit when-not, though the parenthetical clarifies the vault performs this automatically on agent stop or revocation, which implicitly sets expectations about necessity.

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