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Steel MCP Server

Steel MCP Server

by steel-dev
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Hybrid

Interact with the page

steel_act
Destructive

Perform browser actions like clicking, typing, filling forms, selecting, hovering, scrolling, and pressing keys in a live session. Target elements by @eN reference or CSS selector, and get a clear report of what changed.

Instructions

Click, type, fill a form, select an option, hover, scroll, press a key, go back, or dismiss a cookie or consent overlay. Target elements by the @eN reference from steel_snapshot or steel_find, or by a CSS selector. Always reports what actually changed, and says so plainly when nothing did.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "session_id": "<session_id>",
      "action": "<action>"
    },
    "name": "steel_act"
  }
}

Input Schema

NameRequiredDescriptionDefault
valueNoText to type, option to select, key name to press, or scroll distance in pixels.
actionYesWhat to do.
fieldsNoFor fill_form: the fields to fill, in order, in one round trip.
targetNoA @eN reference or a CSS selector. Not needed for scroll, press, go_back or dismiss_overlays.
max_tokensNoCap on the text returned, in tokens. Defaults to 8000.
session_idYesLive session_id from steel_session_create.
include_snapshotNoAlso return the page structure afterwards. Off by default.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Addedv2.0.1

TDQS

A4.2/5.0
Behavior4/5

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

Annotations already provide destructiveHint=true and openWorldHint=true, so the mutation risk is flagged. The description adds value beyond that by promising that the tool always reports what actually changed and says so plainly when nothing did, and by enumerating the side-effecting actions it performs. This is useful behavioral context rather than a contradiction.

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 tight sentences cover the action set, targeting strategy, and output reporting behavior. Every sentence earns its place; there is no filler or repetition of schema details.

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?

For a 7-parameter, 10-action tool with no output schema, the description covers the action set, target syntax, and reporting promise. Operational details like session_id and max_tokens are handled by the schema. The return format is only vaguely described, but the honesty guarantee compensates enough for a tool of this complexity.

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

Parameters3/5

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

Schema description coverage is 100%, so every parameter is already documented in the schema. The description adds only light enrichment, such as mentioning @eN references from steel_snapshot/steel_find and cookie/consent overlays. Since the schema carries the parameter burden, a baseline 3 is appropriate.

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 names a concrete set of interactions—click, type, fill a form, select, hover, scroll, press, go back, dismiss overlays—and ties them to a specific resource: the current page. It also distinguishes itself from siblings like steel_navigate and steel_snapshot by making clear this is the general page-interaction tool.

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 gives clear usage context: target elements by @eN references from steel_snapshot or steel_find, or by CSS selector. This implies the prerequisite of running snapshot/find first and orients the agent to the correct workflow. It does not explicitly state when not to use the tool or name alternatives, but the usage situation is still clear.

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

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