Add a single block to an mBlock project, optionally chaining it after another block. Specify opcode, fields, parameters, position, and target for precise placement.
Add a single block, optionally chained after afterId. Tip: describe_opcode first.
| Name | Required | Description | Default |
|---|---|---|---|
| x | No | ||
| y | No | ||
| path | No | ||
| dryRun | No | ||
| fields | No | ||
| opcode | Yes | ||
| params | No | ||
| target | No | ||
| afterId | No | ||
| confirm | No |
Changes observed during successful MCP inspections.
v1.0.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false, so the basic safety profile is covered. The description adds placement behavior by saying the block can be chained after afterId, but it does not disclose behavior around dryRun, confirm, invalid opcodes, or whether the block is inserted at a default position.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is compact and front-loaded: it states the core action in the first phrase, adds the key placement detail, then gives a practical tip. Every sentence earns its place and there is no filler.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given 10 parameters, nested objects, no output schema, and zero parameter documentation, a two-clause description is not enough for an agent to call the tool confidently. It covers the core purpose and afterId, but leaves most of the input surface undocumented, so completeness is low.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
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 for 10 parameters. It explains a meaningful detail for afterId and hints that opcode matters via the describe_opcode tip, but x, y, path, target, fields, params, dryRun, and confirm remain entirely unexplained.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description states a specific action ('Add') on a specific resource ('a single block'), and the qualifier 'single' plus 'optionally chained after afterId' distinguishes it from related tools like add_script or move_block. It is immediately clear what this tool does and what its unique scope is.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description gives a useful workflow hint ('Tip: describe_opcode first'), which implies the agent should validate opcodes before calling. However, it does not explicitly say when to prefer this over sibling tools like add_script or move_block, nor does it state exclusions or preconditions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.