| 1 | package agent |
| 2 | |
| 3 | import ( |
| 4 | "encoding/json" |
| 5 | "fmt" |
| 6 | "strings" |
| 7 | ) |
| 8 | |
| 9 | // capabilityInputError distinguishes repairable envelope errors from target |
| 10 | // availability and authorization failures without changing their error text. |
| 11 | type capabilityInputError struct{ error } |
| 12 | |
| 13 | func (e *capabilityInputError) Unwrap() error { return e.error } |
| 14 | func capabilityInputErrorf(format string, args ...any) error { |
| 15 | return &capabilityInputError{fmt.Errorf(format, args...)} |
| 16 | } |
| 17 | |
| 18 | type useCapabilityArgs struct { |
| 19 | Action string `json:"action"` |
| 20 | CapabilityID string `json:"capability_id"` |
| 21 | Query string `json:"query"` |
| 22 | Limit int `json:"limit"` |
| 23 | Cursor string `json:"cursor"` |
| 24 | Arguments json.RawMessage `json:"arguments"` |
| 25 | Reason string `json:"reason"` |
| 26 | } |
| 27 | |
| 28 | func parseUseCapabilityArgs(raw json.RawMessage) (useCapabilityArgs, string, string, error) { |
| 29 | var args useCapabilityArgs |
| 30 | if err := json.Unmarshal(raw, &args); err != nil { |
| 31 | return args, "", "", fmt.Errorf("invalid args: %w", err) |
| 32 | } |
| 33 | action := strings.ToLower(strings.TrimSpace(args.Action)) |
| 34 | id := strings.TrimSpace(args.CapabilityID) |
| 35 | if args.Limit < 0 || action == "search" && args.Limit > 8 || action == "list" && args.Limit > 100 { |
| 36 | return args, "", "", fmt.Errorf("limit must be 1..8 for search or 1..100 for list when provided") |
| 37 | } |
| 38 | if action == "call" && strings.HasPrefix(id, "mcp-tool:") { |
| 39 | normalized, err := normalizeMCPToolArguments(args.Arguments) |
| 40 | if err != nil { |
| 41 | return args, "", "", err |
| 42 | } |
| 43 | args.Arguments = normalized |
| 44 | } |
| 45 | return args, action, id, nil |
| 46 | } |
| 47 | |
| 48 | // normalizeMCPToolArguments accepts only an object. It deliberately does not |
| 49 | // unwrap JSON strings, rename fields, coerce values, or guess enums: schema |
| 50 | // mistakes must produce one precise repair contract instead of hidden behavior |
| 51 | // that differs between direct and proxied MCP calls. |
| 52 | func normalizeMCPToolArguments(raw json.RawMessage) (json.RawMessage, error) { |
| 53 | trimmed := strings.TrimSpace(string(raw)) |
| 54 | if trimmed == "" || trimmed == "null" { |
| 55 | return json.RawMessage(`{}`), nil |
| 56 | } |
| 57 | var object map[string]any |
| 58 | if !strings.HasPrefix(trimmed, "{") || json.Unmarshal([]byte(trimmed), &object) != nil || object == nil { |
| 59 | return nil, fmt.Errorf("arguments for an MCP tool must be a JSON object; arrays, scalars, malformed JSON, and nested JSON strings are not supported") |
| 60 | } |
| 61 | return json.RawMessage(append([]byte(nil), trimmed...)), nil |
| 62 | } |
| 63 |