Prism
Give your AI agent the same code intelligence your IDE has.
When an agent navigates your codebase, it guesses: pattern-matching over text with grep and heuristics. Your VS Code workspace already runs language servers (TypeScript, rust-analyzer, Pylance, …) that know the actual answer: exact types, full inheritance chains, cross-file references, live diagnostics. Prism bridges those language servers to your agent via MCP so it stops guessing.
Why it matters
Here's a concrete example. Ask an agent: "Find all implementations of IntrinsicException in the NestJS repo."
| Approach |
Results |
| grep |
6 files (only direct extends/import occurrences) |
Prism find_implementations |
23 implementations, full inheritance chain resolved |
Grep found the files that mention the string. Prism asked the TypeScript language server, which traversed the actual type hierarchy. Both used roughly the same tokens.
Watch the benchmark walkthrough
| Tool |
What it does |
find_references |
Every location that references a symbol, including the declaration site |
go_to_definition |
Declaration location(s) for a symbol |
find_implementations |
Concrete classes or functions implementing an interface or abstract method |
get_type |
Location of the type alias or interface declaration for a symbol |
get_diagnostics |
Errors and warnings for a file (absolute path required) |
list_symbols |
Symbols in the workspace or a single file |
get_call_hierarchy |
Incoming/outgoing call tree up to depth 3 |
Works with any language server registered in VS Code. Tested with TypeScript and rust-analyzer.
How it works
Prism runs inside the VS Code extension host and plays two roles:
- LSP client: delegates to language servers via
vscode.commands.executeCommand. No custom LSP wire protocol.
- MCP server: binds an HTTP server to
localhost:7878. Agents call tools via JSON-RPC 2.0 over POST /.
Language Servers (TypeScript, rust-analyzer, Pylance, …)
↑ LSP wire protocol
VS Code LSP Client (built-in)
↑ vscode.commands.executeCommand(…)
Prism Extension ← this repo
↑ HTTP POST { tool, params }
Agent (MCP client)
Installation
Install the extension from the VS Code marketplace, then reload your window. That's it. Prism starts automatically, and your agent can start using the tools right away.
Configuration
| Key |
Default |
Description |
prism.port |
7878 |
HTTP port. Auto-increments to 7900 if busy; .mcp.json is written with the actual bound port. |
prism.lspRetryCount |
10 |
Max retries waiting for the language server before a tool call fails. |
prism.lspRetryIntervalMs |
1000 |
Milliseconds between retries. |
prism.enabledTools |
all tools |
Not yet implemented. All 7 tools are always active. See Known gaps. |
prism.agent |
"Claude Code" |
MCP client to configure. "Claude Code" writes .mcp.json at the workspace root; "Github Copilot" writes .vscode/mcp.json. |
Known gaps
get_type returns a location, not a type string. executeTypeDefinitionProvider gives the location of the type alias or interface, not an inferred type like string | number. A get_hover tool would be the right path for that.
get_diagnostics only works for already-open files. Files never opened in the editor have no diagnostics in VS Code's in-memory collection, even if they contain errors.
enabledTools is not enforced. The config key is declared but not read — all 7 tools are always active.
prism.reindex cannot verify language server readiness. The command flushes dirty buffers but can't poll the LS for completion. Readiness is discovered on the next tool call via the retry loop.
Timeouts. Tool calls time out after 25 s; the HTTP socket timeout is 30 s.
No streaming. All tool calls are synchronous request/response. Diagnostic changes are not pushed; the agent must poll get_diagnostics.
Architecture
See docs/architecture.md for a walkthrough of symbol resolution, LSP readiness handling, the retry loop, and each tool's implementation.
Contributors
PRs and issues are welcome.
License
MIT
