browser_credential_fill

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

With no annotations provided, the description carries the disclosure burden. It reveals a critical behavioral trait: the tool never receives the secret. This goes beyond typical expectations and is valuable safety information, though it does not detail what happens after the UI is invoked (e.g., blocking behavior, user interaction required).

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?

A single, front-loaded sentence of 14 words conveys the core action and safety constraint. Every word earns its place with no fluff or repetition.

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 tool has nested objects and an enum, with no output schema. The description covers purpose and the key safety aspect, but omits expected behavior after invoking the UI (immediate return vs. waiting for user action) and potential failure modes. Adequate but with clear gaps.

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 only 33%, and the description provides no additional parameter explanations. The locator's schema description is helpful, but the description overall does not compensate for the low coverage—broker choices and collaboration_id semantics are left entirely to the schema.

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 function: "Focus a field and invoke a local password-manager UI" — a specific verb and resource. It also distinguishes itself from siblings by adding the key constraint "without receiving the secret," which sets it apart from browser_type or browser_focus.

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 implies usage for credential filling without exposing secrets, providing clear context. However, it does not explicitly name alternatives (e.g., browser_type, browser_focus) or state when not to use the tool, so guidance is implied rather than explicit.

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