Specky

Generate Devcontainer Config

sdd_generate_devcontainer

Idempotent

Generates .devcontainer/devcontainer.json by detecting your project's tech stack, enabling consistent development environments in VS Code Dev Containers or GitHub Codespaces.

Instructions

Generates .devcontainer/devcontainer.json from the detected tech stack (codebase manifests, falling back to DESIGN.md). Writes the file to disk for local use with VS Code Dev Containers or GitHub Codespaces.

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": "sdd_generate_devcontainer"
  }
}

Input Schema

Name	Required	Description	Default
`features`	No	Devcontainer features to include (e.g., 'ghcr.io/devcontainers/features/node:1').
`spec_dir`	No	Spec directory path (relative to workspace root)	.specs
`base_image`	No	Base Docker image for the devcontainer. Auto-detected from tech stack if omitted.
`feature_number`	No	Feature number (zero-padded, e.g. '001')	001

Schema Changelog

Changes observed during successful MCP inspections.

First observedv3.4.0-rc.14May 3, 2026

TDQS

A3.8/5.0

Behavior3/5

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

Annotations already declare idempotentHint=true and destructiveHint=false. The description adds that the tool 'writes the file to disk', which is consistent with a non-destructive write. However, it does not mention overwrite behavior or potential side effects like modifying existing configs without confirmation. Given annotations cover safety profile, the description provides adequate but not exceptional transparency.

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 two sentences long, front-loaded with the primary action and source. Every sentence adds value without redundancy. It is concise and well-structured for quick understanding.

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?

The description explains the output file's contents (base image, features, extensions, port forwarding) and the detection mechanism. Without an output schema, this is sufficient for an agent to understand what the tool produces. However, it could mention that the tool creates the .devcontainer directory if missing.

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 coverage is 100% as all four parameters have descriptions in the input schema. The description adds minimal extra meaning beyond the schema, only implying that features and base_image are configurable. Baseline 3 is appropriate since the description does not significantly enhance parameter understanding.

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?

The description clearly states the tool generates .devcontainer/devcontainer.json from the detected tech stack. It specifies the verb 'generates', the resource 'devcontainer config', and the source 'codebase manifests, falling back to DESIGN.md'. This is specific and distinct from sibling tools like sdd_generate_dockerfile.

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 description mentions the output is for local use with VS Code Dev Containers or GitHub Codespaces, which implies usage context. However, it does not explicitly state when to use this tool versus alternatives (e.g., sdd_generate_dockerfile) or when not to use it. No comparison or exclusion criteria are provided.

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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