scratch-unified-mcp

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Sb3 Get Block Schema

sb3_get_block_schema

Retrieve the full block schema for a specific Scratch opcode, including shadow encodings, to validate or construct custom blocks in project editing workflows.

Instructions

Full schema for one opcode incl. shadow encodings. (proxied)

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": {
      "opcode": "<opcode>"
    },
    "name": "sb3_get_block_schema"
  }
}

Input Schema

Name	Required	Description	Default
`opcode`	Yes
`target`	No

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Sep 19, 2026

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 context. It does disclose that the operation is '(proxied)' and that it returns the full schema, but it does not describe error behavior, scope, or any limitations of the proxy.

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 concise and front-loaded, carrying the core purpose plus a useful proxying note with no filler.

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?

The output schema covers return shape, and the operation is small, but the description omits the meaning of the optional target parameter and how opcode values are obtained. Minimal but viable for an agent that already knows the opcode.

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

Parameters2/5

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

Schema coverage is 0%, so the description must explain parameters. It clarifies that 'opcode' selects one opcode, but it says nothing about the 'target' parameter or valid opcode values/formats, leaving the agent to guess.

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 states the resource clearly: 'Full schema for one opcode incl. shadow encodings', which is more informative than the tool name alone. It does not explicitly contrast with block-listing/finding siblings, so it loses the top point.

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?

The phrase 'for one opcode' implies the use case of retrieving a single opcode's schema, but the description gives no explicit when-to-use/when-not-to-use guidance or mention of alternatives among the many sb3 tools.

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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