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 | ||
| } | ||
|
|
||
| return nil | ||
| }, | ||
| } |
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| Original file line number | Diff line number | Diff line change | ||||||||||||
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| @@ -0,0 +1,195 @@ | ||||||||||||||
| 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 stringified var, got: %v", key)) | ||||||||||||||
| } | ||||||||||||||
|
Comment on lines
+55
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+58
There was a problem hiding this comment. Fix error message: report the offending value/type, not the key. - value, ok := rawValue.(string)
- if !ok {
- return map[string]string{}, mcp.NewToolResultError(fmt.Sprintf("Expected stringified var, got: %v", key))
- }
+ value, ok := rawValue.(string)
+ if !ok {
+ return map[string]string{}, mcp.NewToolResultError(fmt.Sprintf("Variable %q must be a string, got: %T", key, rawValue))
+ }🤖 Prompt for AI Agents |
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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{}{}, | ||||||||||||||
|
There was a problem hiding this comment. we'll add feature flags in future releases |
||||||||||||||
| ) | ||||||||||||||
| if iErr != nil { | ||||||||||||||
| mcp.NewToolResultError(iErr.Error()) | ||||||||||||||
| } | ||||||||||||||
| 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 modelling finantial transaction in an easy and declarative way. Numscript scripts alwasy terminate. | ||||||||||||||
| `), | ||||||||||||||
|
Comment on lines
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+183
There was a problem hiding this comment. Typos in instructions string. Correct spelling/grammar to avoid user-facing nits: - server.WithInstructions(`
- You're a numscript expert AI assistant. Numscript is a DSL that allows modelling finantial transaction in an easy and declarative way. Numscript scripts alwasy terminate.
- `),
+ 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.
+ `),📝 Committable suggestion
Suggested change
🤖 Prompt for AI Agents |
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| // TODO add prompt | ||||||||||||||
|
There was a problem hiding this comment. we can add a more complete prompt in future releases |
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| ) | ||||||||||||||
| 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: