Generates and writes DESIGN.md with architecture overview, Mermaid diagrams, ADRs, and API contracts.
AI agents use sdd_write_design to create or update resources in Specky — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Specky environment.
This tool creates or modifies design documentation files (DESIGN.md), which is a reversible write operation. While it generates substantial artifacts that could influence downstream development decisions, the action itself is non-destructive and can be overwritten or reverted.
From the tool's definition Tool description states it 'Generates and writes DESIGN.md' — the verb 'writes' indicates creation/modification of files. The output includes architecture documentation, diagrams, ADRs (Architecture Decision Records), and API contracts.
Documented attack patterns abuse exactly the kind of access sdd_write_design gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Specky, and nothing reaches the server without passing your rules. This is the rule we recommend for sdd_write_design:
{
"version": "1",
"default": "deny",
"tools": {
"sdd_write_design": {
"limits": [
{
"counter": "sdd_write_design_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}sdd_write_design stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
Free to start. No card required.
Generates and writes DESIGN.md with architecture overview, Mermaid diagrams, ADRs, and API contracts. It is categorised as a Write tool in the Specky MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Specky MCP server in PolicyLayer and add a rule for sdd_write_design: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Specky. Nothing to install.
sdd_write_design is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the sdd_write_design rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for sdd_write_design. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
sdd_write_design is provided by the Specky MCP server (paulasilvatech/specky). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Specky, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
56 Specky tools catalogued and risk-classified — across an index of 43,000+ MCP servers.