Substructure
just TOML and webhooks
Last checked:
What is Substructure?
Substructure is a platform for rapidly building and deploying AI agents that integrate with Slack. It allows developers to configure agents using TOML, bring their own LLM provider, connect MCP servers for tool access, and customize agent behavior through webhooks. Agents can be developed locally and self-hosted.
Substructure pricing
Pricing model: Freemium
Substructure pros
- Quick setup with CLI and TOML configuration
- Bring-your-own-LLM support (Anthropic, OpenAI, OpenRouter)
- Built-in MCP server integration with automatic authorization and tool execution
- Complete agent loop customization via webhooks
- Local development and testing before deployment
- Self-hostable open-source engine
- AG-UI protocol support for multiple client interfaces (assistant-ui, CopilotKit)
Substructure cons
- Slack-centric design; limited built-in integrations beyond Slack
- No explicit free tier or pricing information provided
- Requires technical setup knowledge (CLI, TOML, webhooks, potentially custom workers)
Frequently asked questions about Substructure
Can I use my own LLM provider?
Yes, Substructure supports Anthropic, OpenAI, and OpenRouter. You provide your own API keys, which the engine uses on your behalf.
Does it integrate with Slack?
Yes, Slack is the primary integration. You can configure agents to respond to direct messages or mentions in Slack channels.
Can I customize how agents behave?
Yes, through webhooks. You can handle decision requests and customize every step of the agent loop, or build custom tools in your own worker.
Can I run this locally?
Yes, use `subs serve` to run the engine locally for development and testing before going live.
What are MCP servers and does Substructure support them?
MCP (Model Context Protocol) servers provide tools for agents. Substructure has built-in support—it handles authorization and executes every tool call securely.