feat: MCP first MVP #97
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,22 @@ | ||
| package cmd | ||
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| import ( | ||
| "github.com/formancehq/numscript/internal/mcp_impl" | ||
| "github.com/spf13/cobra" | ||
| ) | ||
|
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| var mcpCmd = &cobra.Command{ | ||
| Use: "mcp", | ||
| Short: "Run the mcp server", | ||
| Hidden: true, | ||
| RunE: func(cmd *cobra.Command, args []string) error { | ||
| err := mcp_impl.RunServer() | ||
| if err != nil { | ||
| cmd.SilenceErrors = true | ||
| cmd.SilenceUsage = true | ||
| return err | ||
| } | ||
|
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| return nil | ||
| }, | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,194 @@ | ||
| package mcp_impl | ||
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| import ( | ||
| "context" | ||
| "fmt" | ||
| "math/big" | ||
| "strings" | ||
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| "github.com/formancehq/numscript/internal/analysis" | ||
| "github.com/formancehq/numscript/internal/interpreter" | ||
| "github.com/formancehq/numscript/internal/parser" | ||
| "github.com/mark3labs/mcp-go/mcp" | ||
| "github.com/mark3labs/mcp-go/server" | ||
| ) | ||
|
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| func parseBalancesJson(balancesRaw any) (interpreter.Balances, *mcp.CallToolResult) { | ||
| balances, ok := balancesRaw.(map[string]any) | ||
| if !ok { | ||
| return interpreter.Balances{}, mcp.NewToolResultError(fmt.Sprintf("Expected an object as balances, got: <%#v>", balancesRaw)) | ||
| } | ||
|
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| iBalances := interpreter.Balances{} | ||
| for account, assetsRaw := range balances { | ||
| if iBalances[account] == nil { | ||
| iBalances[account] = interpreter.AccountBalance{} | ||
| } | ||
|
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| assets, ok := assetsRaw.(map[string]any) | ||
| if !ok { | ||
| return interpreter.Balances{}, mcp.NewToolResultError(fmt.Sprintf("Expected nested object for account %v", account)) | ||
| } | ||
|
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| for asset, amountRaw := range assets { | ||
| amount, ok := amountRaw.(float64) | ||
| if !ok { | ||
| return interpreter.Balances{}, mcp.NewToolResultError(fmt.Sprintf("Expected float for amount: %v", amountRaw)) | ||
| } | ||
|
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| n, _ := big.NewFloat(amount).Int(new(big.Int)) | ||
| iBalances[account][asset] = n | ||
| } | ||
| } | ||
| return iBalances, nil | ||
| } | ||
|
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| func parseVarsJson(varsRaw any) (map[string]string, *mcp.CallToolResult) { | ||
| vars, ok := varsRaw.(map[string]any) | ||
| if !ok { | ||
| return map[string]string{}, mcp.NewToolResultError(fmt.Sprintf("Expected an object as vars, got: <%#v>", varsRaw)) | ||
| } | ||
|
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| iVars := map[string]string{} | ||
| for key, rawValue := range vars { | ||
|
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| value, ok := rawValue.(string) | ||
| if !ok { | ||
| return map[string]string{}, mcp.NewToolResultError(fmt.Sprintf("Expected %s var to be a string, got: %T instead", key, rawValue)) | ||
| } | ||
|
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| iVars[key] = value | ||
| } | ||
|
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| return iVars, nil | ||
| } | ||
|
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| func addEvalTool(s *server.MCPServer) { | ||
| tool := mcp.NewTool("evaluate", | ||
| mcp.WithDescription("Evaluate a numscript program"), | ||
| mcp.WithIdempotentHintAnnotation(true), | ||
| mcp.WithReadOnlyHintAnnotation(true), | ||
| mcp.WithOpenWorldHintAnnotation(false), | ||
| mcp.WithString("script", | ||
| mcp.Required(), | ||
| mcp.Description("The numscript source"), | ||
| ), | ||
| mcp.WithObject("balances", | ||
| mcp.Required(), | ||
| mcp.Description(`The accounts' balances. A nested map from the account name, to the asset, to its integer amount. | ||
| For example: { "alice": { "USD/2": 100, "EUR/2": -42 }, "bob": { "BTC": 1 } } | ||
| `), | ||
| ), | ||
| mcp.WithObject("vars", | ||
| mcp.Required(), | ||
| mcp.Description(`The stringified variables to be passed to the script's "vars" block. | ||
| For example: { "acc": "alice", "mon": "EUR 100" } can be passed to the following script: | ||
| vars { | ||
| monetary $mon | ||
| account $acc | ||
| } | ||
|
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| send $mon ( | ||
| source = $acc | ||
| destination = @world | ||
| ) | ||
| `), | ||
| ), | ||
| ) | ||
| s.AddTool(tool, func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) { | ||
| script, err := request.RequireString("script") | ||
| if err != nil { | ||
| return mcp.NewToolResultError(err.Error()), nil | ||
| } | ||
|
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| parsed := parser.Parse(script) | ||
| if len(parsed.Errors) != 0 { | ||
| out := make([]string, len(parsed.Errors)) | ||
| for index, err := range parsed.Errors { | ||
| out[index] = err.Msg | ||
| } | ||
| mcp.NewToolResultError(strings.Join(out, ", ")) | ||
| } | ||
|
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| balances, mcpErr := parseBalancesJson(request.GetArguments()["balances"]) | ||
| if mcpErr != nil { | ||
| return mcpErr, nil | ||
| } | ||
|
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| vars, mcpErr := parseVarsJson(request.GetArguments()["vars"]) | ||
| if mcpErr != nil { | ||
| return mcpErr, nil | ||
| } | ||
|
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| out, iErr := interpreter.RunProgram( | ||
| ctx, | ||
| parsed.Value, | ||
| vars, | ||
| interpreter.StaticStore{ | ||
| Balances: balances, | ||
| }, | ||
| map[string]struct{}{}, | ||
|
Contributor
Author
There was a problem hiding this comment. we'll add feature flags in future releases |
||
| ) | ||
| if iErr != nil { | ||
| return mcp.NewToolResultError(iErr.Error()), nil | ||
| } | ||
| return mcp.NewToolResultJSON(*out) | ||
| }) | ||
| } | ||
|
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| func addCheckTool(s *server.MCPServer) { | ||
| tool := mcp.NewTool("check", | ||
| mcp.WithDescription("Check a program for parsing error or static analysis errors"), | ||
| mcp.WithIdempotentHintAnnotation(true), | ||
| mcp.WithReadOnlyHintAnnotation(true), | ||
| mcp.WithOpenWorldHintAnnotation(false), | ||
| mcp.WithString("script", | ||
| mcp.Required(), | ||
| mcp.Description("The numscript source"), | ||
| ), | ||
| ) | ||
|
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| s.AddTool(tool, func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) { | ||
| script, err := request.RequireString("script") | ||
| if err != nil { | ||
| return mcp.NewToolResultError(err.Error()), nil | ||
| } | ||
|
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| checkResult := analysis.CheckSource(script) | ||
|
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| var errors []any | ||
| for _, d := range checkResult.Diagnostics { | ||
| errors = append(errors, map[string]any{ | ||
| "kind": d.Kind.Message(), | ||
| "severity": analysis.SeverityToString(d.Kind.Severity()), | ||
| "span": d.Range, | ||
| }) | ||
| } | ||
|
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| return mcp.NewToolResultJSON(map[string]any{ | ||
| "errors": errors, | ||
| }) | ||
| }) | ||
| } | ||
|
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| func RunServer() error { | ||
| // Create a new MCP server | ||
| s := server.NewMCPServer( | ||
| "Numscript", | ||
| "0.0.1", | ||
| server.WithToolCapabilities(false), | ||
| server.WithRecovery(), | ||
| server.WithInstructions(` | ||
| You're a Numscript expert AI assistant. Numscript is a DSL that allows modeling financial transactions in an easy and declarative way. Numscript scripts always terminate. | ||
| `), | ||
| ) | ||
| addEvalTool(s) | ||
| addCheckTool(s) | ||
|
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| // Start the server | ||
| if err := server.ServeStdio(s); err != nil { | ||
| return err | ||
| } | ||
|
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| return nil | ||
| } | ||
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Amounts parsing risks precision loss and silently truncates fractions. Enforce integer semantics and accept safe types.
Apply:
Additionally, add import: