browser_fill_secret

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

With no annotations, the description must carry the burden. It discloses the important security behavior (secrets never accepted/returned) but omits other behavioral details such as side effects (e.g., form submission), requirements (visible element), or error conditions. Adequate but not comprehensive.

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 extremely concise—two sentences that front-load the purpose and immediately state a critical constraint. Every word earns its place, with no fluff.

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 that interacts with the browser, the description lacks context: it does not mention that 'ref' comes from browser_snapshot, nor what happens after filling (e.g., does it submit the form?). There is no output schema to compensate. The description is minimal but leaves key workflow 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 100%, so the baseline is 3. The description adds little beyond the schema: it mentions 'secret alias' which matches the schema's description, but does not elaborate on 'ref' or 'field'. It adds marginal value.

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 action ('Fill a username or password field') and the source ('server-side credential broker'). It implicitly distinguishes from sibling tools like browser_fill_form by focusing on secret fields, making the purpose unambiguous.

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 provides one key guideline (pass only a secret alias, never actual secret values) but does not explicitly contrast with alternatives like browser_fill_form or browser_login, nor does it state when to use this tool over others. Usage context 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.