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a11y-toolkit

a11y-toolkit

by kinti
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

a11y-toolkit: Staging vs production diff

a11y_diff_urls
Read-onlyIdempotent

Compare accessibility snapshots of two URLs in one call, such as staging versus production, to reveal WCAG differences between live pages.

Instructions

Snapshot two URLs and diff them in a single call (e.g. staging vs production). Requires local Playwright. — Convenience for staging-vs-production; manual control is snapshot + a11y_diff. Returns the same diff shape as a11y_diff, for two live URLs.

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": {
      "url_a": "<url_a>",
      "url_b": "<url_b>"
    },
    "name": "a11y_diff_urls"
  }
}

Input Schema

NameRequiredDescriptionDefault
url_aYesFirst URL (usually staging)
url_bYesSecond URL (usually production)
auth_stateNoPath to a Playwright storage_state JSON (exported session) to audit behind login — stays local

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv5.5.0
    • addedInput schema / properties / auth_state
      Added value: +{
+  "description": "Path to a Playwright storage_state JSON (exported session) to audit behind login — stays local",
+  "type": "string"
+}
  2. Changed2 schema fields changedv4.0.0
    • addedInput schema / properties / url_a / description
      Added value: +"First URL (usually staging)"
    • addedInput schema / properties / url_b / description
      Added value: +"Second URL (usually production)"
  3. First observedv2.3.0

TDQS

A4.1/5.0
Behavior4/5

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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds useful non-annotation context: a hard dependency on local Playwright, that the auth_state session 'stays local', and that the return shape matches a11y_diff.

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?

Short and front-loaded with the core action and example. The em-dash fragment ('Convenience for...; manual control is...') is slightly choppy but each piece carries information.

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?

With no output schema, the description compensates by stating the return shape matches a11y_diff, and it discloses the Playwright prerequisite. Adequate for a 3-param tool, though it says nothing about failure behavior when a URL is unreachable.

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 the schema already documents all three parameters. The description reinforces the 'two live URLs' and staging-vs-production framing but adds no format or constraint detail beyond the schema, making the baseline 3 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?

States a specific compound verb+resource ('snapshot two URLs and diff them in a single call') and explicitly differentiates from the sibling path (a11y_snapshot + a11y_diff). An agent can tell exactly what this is without opening the schema.

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?

Names the alternative workflow and frames this as the convenience path for staging-vs-production. It gives clear context for selection but stops short of stating explicit when-not-to-use conditions.

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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