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umbra

umbra

by lxchx
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Remote

Block Urls

block_urls

Block URL patterns by wildcard on a browser tab to skip trackers and heavy assets; pass an empty list to clear blocks.

Instructions

Block URL patterns (wildcards). [] to clear. Speed up + skip trackers/heavy assets.

Ex: block_urls('t0', ['googletag', '*.gif']) → {"blocked_patterns":2}

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": {
      "tab_id": "<tab_id>",
      "patterns": "<patterns>"
    },
    "name": "block_urls"
  }
}

Input Schema

NameRequiredDescriptionDefault
tab_idYes
patternsYes

Output Schema

NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

B3.4/5.0
Behavior3/5

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

There are no annotations, so the description carries the full behavioral burden. It usefully discloses wildcard matching, that [] clears patterns, and an example result count, but it does not clarify whether non-empty calls replace or append to existing rules, whether blocking is persistent, or what tab scope means.

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 short, front-loaded with the core action, and includes a concrete example without unnecessary prose. Every fragment contributes either purpose, clearing behavior, or parameter illustration.

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

Completeness2/5

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

For a mutation-style blocking tool with no annotations and 0% schema description coverage, important context is missing: whether patterns replace or extend existing blocks, tab-level persistence, wildcard scope, and error/edge behavior. The output schema covers the return shape, but the call semantics remain under-specified.

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 0%, so the description must compensate. It explains the patterns argument reasonably well via wildcard syntax, [] clearing, and an example, but tab_id is only shown in the example as 't0' and is not explicitly described.

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

Purpose4/5

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

The description gives a specific verb and resource: block URL patterns using wildcards, and it explains the practical purpose of speeding up pages by skipping trackers/heavy assets. It is clear on its own, but it does not distinguish itself from related route/blocking siblings such as route_block_set or route_add.

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

Usage Guidelines3/5

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

It implies when to use the tool by naming speed-up, tracker skipping, and heavy-asset avoidance, and it notes that an empty list clears patterns. However, it gives no explicit when-not guidance and does not mention alternatives such as route_block_set or route_add.

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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