Model Context Protocol in OCaml
anil.recoil.org
1open Mcp
2open Mcp_sdk
3
4(* Helper for extracting string value from JSON *)
5let get_string_param json name =
6 match json with
7 | `Assoc fields ->
8 (match List.assoc_opt name fields with
9 | Some (`String value) -> value
10 | _ -> raise (Failure (Printf.sprintf "Missing or invalid parameter: %s" name)))
11 | _ -> raise (Failure "Expected JSON object")
12
13(* Create a server *)
14let server = create_server
15 ~name:"OCaml MCP Capitalizer"
16 ~version:"0.1.0"
17 ~protocol_version:"2024-11-05" () |>
18 fun server ->
19 (* Set default capabilities *)
20 configure_server server ~with_tools:true ~with_resources:true ~with_prompts:true ()
21
22(* Define and register a capitalize tool *)
23let _ = add_tool server
24 ~name:"capitalize"
25 ~description:"Capitalizes the provided text"
26 ~schema_properties:[
27 ("text", "string", "The text to capitalize")
28 ]
29 ~schema_required:["text"]
30 (fun args ->
31 try
32 let text = get_string_param args "text" in
33 let capitalized_text = String.uppercase_ascii text in
34 TextContent.yojson_of_t TextContent.{
35 text = capitalized_text;
36 annotations = None
37 }
38 with
39 | Failure msg ->
40 Log.errorf "Error in capitalize tool: %s" msg;
41 TextContent.yojson_of_t TextContent.{
42 text = Printf.sprintf "Error: %s" msg;
43 annotations = None
44 }
45 )
46
47(* Define and register a resource example *)
48let _ = add_resource server
49 ~uri_template:"greeting://{name}"
50 ~description:"Get a greeting for a name"
51 ~mime_type:"text/plain"
52 (fun params ->
53 match params with
54 | [name] -> Printf.sprintf "Hello, %s! Welcome to the OCaml MCP server." name
55 | _ -> "Hello, world! Welcome to the OCaml MCP server."
56 )
57
58(* Define and register a prompt example *)
59let _ = add_prompt server
60 ~name:"capitalize-prompt"
61 ~description:"A prompt to help with text capitalization"
62 ~arguments:[
63 ("text", Some "The text to be capitalized", true)
64 ]
65 (fun args ->
66 let text =
67 try
68 List.assoc "text" args
69 with
70 | Not_found -> "No text provided"
71 in
72 [
73 Prompt.{
74 role = `User;
75 content = Mcp.make_text_content "Please help me capitalize the following text:"
76 };
77 Prompt.{
78 role = `User;
79 content = Mcp.make_text_content text
80 };
81 Prompt.{
82 role = `Assistant;
83 content = Mcp.make_text_content "Here's the capitalized version:"
84 };
85 Prompt.{
86 role = `Assistant;
87 content = Mcp.make_text_content (String.uppercase_ascii text)
88 }
89 ]
90 )
91
92let () =
93 (* Run the server with the default scheduler *)
94 Eio_main.run @@ fun env->
95 Mcp_server.run_server env server