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SnapSurf

SnapSurf

Official
by zumerlab
OverviewSchemaSourceRelated ServersDiscussionsAdmin
JavaScript
Local

Scroll without acting

browser_scroll
Read-onlyIdempotent

Scroll the browser viewport to an element, top, bottom, or pixel offset to load lazy content, then use browser_verify to inspect the updated page.

Instructions

Scroll WITHOUT acting: by element id (to center), to "top"/"bottom", or to an absolute y in pixels. The one legitimate reason: dense listings hydrate their content lazily on scroll and the semantic walk honestly sees only the DOM that exists — scroll, then browser_verify to see what appeared. Ids from the current observation remain valid (scrolling does not re-observe). Includes a bounded settle for the lazy loaders.

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": {
      "target": "<target>"
    },
    "name": "browser_scroll"
  }
}

Input Schema

NameRequiredDescriptionDefault
targetYesid n_xxx, "top", "bottom", or a y offset in pixels
sessionIdNooptional: the session this call belongs to (from browser_session_open). Omitted uses the shared default session.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.1

TDQS

A4.6/5.0
Behavior5/5

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

Beyond the annotations (read-only, idempotent, non-destructive), the description adds important behavioral details: it does not re-observe the DOM ('scrolling does not re-observe'), includes a 'bounded settle' for lazy loaders, and clarifies that element ids remain valid. These traits are not in the annotations and significantly aid the agent's understanding.

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

Conciseness4/5

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

The description is concise and front-loaded, with the key purpose stated first. It includes some stylistic flourishes (e.g., 'the semantic walk honestly sees only the DOM that exists') that add a bit of verbosity but do not obscure the meaning. Overall, it is well-structured and efficient.

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

Completeness5/5

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

Given the tool's simplicity and the lack of an output schema, the description is complete. It covers when to use the tool, behavioral expectations, parameter usage, and a recommended follow-up action. No critical information is missing for an agent to use it effectively.

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?

The schema already provides full descriptions for both parameters with 100% coverage. The description reiterates the target types but adds little new parameter-specific information beyond the schema, such as the 'to center' detail and the note about id validity, which are more behavioral than semantic. Thus, it meets the baseline for high schema coverage but does not elevate it.

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 tool scrolls the page, explicitly distinguishing it from acting ('Scroll WITHOUT acting') and specifying the three target types (element id, top/bottom, pixel offset). It also provides a legitimate use case, 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.

Usage Guidelines5/5

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

The description gives explicit guidance on when to use this tool: for lazy-loading content, with a follow-up suggestion to use browser_verify to check what appeared. It implies alternatives by contrasting with 'acting' and mentions the DOM re-observation behavior, which helps the agent decide when this tool is appropriate.

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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