nex_browser_fill_credentials

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

With no annotations, the description carries the burden and does so well: it discloses the security trade-off of literal values, the no-storage/no-repeat constraint, and the no-submit behavior. It stops short of describing failure modes (e.g., stale snapshot refs, invisible or missing target fields) that matter for a DOM-mutating tool.

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 tight sentences: capability first, alternative plus rationale second, safety constraint third. No filler and nothing buried.

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?

No output schema and no annotations, so the description must stand alone; it covers purpose, alternative routing, and the key safety constraints. It leaves some gaps around error behavior and field-matching when targets are omitted, which an 8-param mutation tool ideally would address.

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 is 63%, with target-ref semantics documented in the schema itself; the description adds the 'visible fields' constraint but says nothing about the username/password/totpCode pairing or how omitted targets are resolved. Baseline 3 applies since the schema does most of the work.

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 — filling literal login credentials into visible fields — and scopes it to values the user explicitly supplied in the current request. It is clearly separable from nex_browser_fill_account and nex_browser_fill_form.

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?

Explicitly routes the agent: prefer nex_browser_fill_account when a stored vault credential exists, and gives the reason (literal values cross the model/MCP request boundary). It also states the terminal condition that the form is never submitted.

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