veilbrowser

veil_back

Navigate back one entry in session history, with optional wait for page load or network idle.

Instructions

Go back one entry in session history (errors if there's nothing earlier). waitUntil 'load' (default) or 'networkidle'.

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_back"
  }
}

Input Schema

Name	Required	Description	Default
`waitUntil`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.5.0Jul 29, 2026

TDQS

A4.3/5.0

Behavior3/5

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

With no annotations provided, the description carries the full burden. It discloses the error condition (nothing earlier) and the waitUntil behavior (load/networkidle). However, it does not mention side effects like triggering navigation or reloading the page, which might be important for an agent to know.

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?

The description is concise with two sentences. The first sentence covers the primary purpose and error behavior, while the second adds critical parameter detail. No redundant information, and it is front-loaded with the most important action.

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?

The tool is simple with only one parameter and no output schema. The description covers the action, error behavior, and parameter options. It implicitly assumes the agent knows about browser session history, which is reasonable. A brief mention of prerequisites (e.g., must have prior navigation) would improve completeness, but it's adequate.

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

Parameters5/5

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

The input schema has one parameter with enum values but no description. The tool description adds significant value by explaining the default ('load') and the two options ('load' or 'networkidle'), which is essential for correct usage. Schema coverage is 0%, so description fully compensates.

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?

The description clearly states the action ('go back one entry in session history') and the specific resource (session history). It also mentions error behavior when no history, which distinguishes it from siblings like veil_forward (go forward) and veil_goto (navigate to URL).

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

Usage Guidelines4/5

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

The description explicitly mentions the `waitUntil` parameter with its default and alternatives, providing guidance on how to use the tool. However, it does not explicitly state when to use this tool vs. alternatives, though the context of going back in history is clear from the purpose.

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