veilbrowser

veil_fedcm_signin

Complete federated login (Sign in with Google, FedCM) by waiting for the native account chooser and selecting an account. Use triggerRef for active sign-in buttons; omit for passive flows.

Instructions

Complete a federated ('Sign in with Google', FedCM) login that Chrome renders as a native chooser no click can reach: waits for the intercepted account chooser, selects an account, and returns it. Pass triggerRef to first click an active sign-in button; omit it for one-tap/passive flows (call veil_fedcm_enable before navigating). accountIndex defaults to 0.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "veil_fedcm_signin"
  }
}

Input Schema

Name	Required	Description	Default
`triggerRef`	No
`accountIndex`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.5.0Jul 29, 2026

TDQS

A4.6/5.0

Behavior4/5

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

Describes blocking behavior (waits for chooser, selects account, returns it). Mentions default accountIndex. But does not specify timeout or error handling if no account appears. Still, adequate for a straightforward interactive tool.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences, well-structured. Front-loaded with main purpose, then details on parameters and variations. No redundant or extra words.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given no annotations, no output schema, and only 2 optional parameters, the description covers purpose, usage, parameters, and behavioral aspects. Lacks potential error scenarios or return format, but still largely complete.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 0%, so description must compensate. Explains triggerRef as referencing an active sign-in button and accountIndex defaulting to 0. Lacks detail on triggerRef type (e.g., how to obtain it), but adds meaningful usage context.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

Purpose is clearly stated: completes a federated login (FedCM), waits for account chooser, selects an account, returns it. Differentiates from sibling veil_fedcm_enable by mentioning its role in passive flows.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly explains when to pass triggerRef (active button click) vs omit it (one-tap/passive flows). Also directs to call veil_fedcm_enable before navigating for passive flows, providing clear alternative guidance.

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