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scratch-unified-mcp

scratch-unified-mcp

by blessed0x
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

Sb3 List Blocks

sb3_list_blocks

List standard Scratch VM opcodes, optionally filtered by category, to identify available block types for editing or building projects.

Instructions

Catalog of standard opcodes from scratch-vm, optionally by category. (proxied)

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": "sb3_list_blocks"
  }
}

Input Schema

NameRequiredDescriptionDefault
categoryNo

Output Schema

NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.0.0

TDQS

B3.3/5.0
Behavior3/5

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

With no annotations, the description must carry behavioral weight. It usefully states that this is a proxied catalog sourced from scratch-vm and can be filtered by category, implying a read-only operation. However, it does not explain category value handling, failure behavior, or what counts as 'standard' beyond the source.

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 a single, front-loaded sentence with no filler. It states the resource, the optional filtering behavior, and the proxied nature in very few words.

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

Completeness3/5

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

For a simple one-optional-parameter tool with an output schema, the description is minimally viable: it says what is returned and that category can filter it. But it omits any comparison to sibling tools and leaves category vocabulary unspecified, so context is not fully complete.

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 has one parameter 'category' with 0% description coverage, so the description must compensate. 'Optionally by category' does clarify that the parameter filters the catalog, but it does not enumerate valid values or define behavior for unknown categories. This is minimal compensation.

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 identifies a concrete resource ('standard opcodes from scratch-vm') and an optional modifier ('by category'), which makes the tool's purpose understandable. It lacks an explicit verb and does not differentiate it from sibling block-related tools, but the catalog/list intent is clear.

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

Usage Guidelines2/5

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

No guidance is given for when to use this tool versus alternatives such as sb3_get_block_schema, sb3_find_blocks, or spy_list_block_types. The only usage hint is that category filtering is optional, which is not enough to route an agent.

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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