[FEATURE]: Lazy/dynamic loading for mcp tools #8277
Description
Feature hasn't been suggested before.
- I have verified this feature I'm about to request hasn't been suggested before.
Describe the enhancement you want to request
Problem
When multiple MCP servers are enabled, all tool definitions load into the agent's context at session startup. A single MCP server like GitHub can add 15-20k+ tokens just for tool schemas. With several MCPs enabled, context bloat can exceed 50k tokens before the user even sends a message. This is even mentioned in the docs: https://opencode.ai/docs/mcp-servers/
Solution
Lazy loading pattern: Instead of loading full tool schemas at startup, we:
Show a lightweight index in the system prompt with server names and tool names only (~150 tokens vs ~1.5k)
Provide a mcp_load_tools meta-tool that loads specific tools on-demand
The agent loop naturally picks up newly loaded tools on the next iteration
Example Flow
System prompt shows:
"playwright (20 tools): browser_snapshot, browser_click, browser_navigate, ..."
User: "Take a screenshot of google.com"
Agent calls: mcp_load_tools("playwright", ["browser_navigate", "browser_snapshot"])
→ Tools loaded into session state
Agent calls: playwright_browser_navigate({ url: "https://google.com/" })
Agent calls: playwright_browser_snapshot()
Related
- Addresses: Option to Enable / Disable MCP Servers (via TUI) #514, Enable/Disable MCP server by Mode #1101, Feature Request: Global default tools configuration for agents #2888, [feature request]: ability to dynamic turn on mcp server for specific agent #2953, [FEATURE]: Option to deny MCP tools by default #3612, [FEATURE]: Allow to enable MCP on a per-agent basis #5373, [FEATURE]: Provider/Model-specific MCP servers #6024