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more mcp fiddling #5535

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59 changes: 31 additions & 28 deletions packages/darklang/languageTools/mcp-server/initialize.dark
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Original file line number Diff line number Diff line change
Expand Up @@ -14,40 +14,43 @@ let handleInitializeRequest
: McpState =
log "Handling initialize request"

// Build server capabilities
// Build server capabilities using proper types
let serverCapabilities =
Json.Object [
("resources", Json.Object [
("subscribe", Json.Bool false);
("listChanged", Json.Bool true)
]);
("tools", Json.Object [
("listChanged", Json.Bool true)
]);
("prompts", Json.Object [
("listChanged", Json.Bool true)
]);
("logging", Json.Object []);
("roots", Json.Object [
("listChanged", Json.Bool true)
])
]
ModelContextProtocol.ServerCapabilities {
resources = Stdlib.Option.Option.Some (ModelContextProtocol.ResourceCapabilities {
listChanged = Stdlib.Option.Option.Some true;
subscribe = Stdlib.Option.Option.Some false
});
tools = Stdlib.Option.Option.Some (ModelContextProtocol.ToolCapabilities {
listChanged = Stdlib.Option.Option.Some true
});
prompts = Stdlib.Option.Option.Some (ModelContextProtocol.PromptCapabilities {
listChanged = Stdlib.Option.Option.Some true
});
logging = Stdlib.Option.Option.Some (Json.Object []);
completions = Stdlib.Option.Option.None;
experimental = Stdlib.Option.Option.None
}

let serverInfo =
Json.Object [
("name", Json.String "Darklang MCP Server");
("version", Json.String "1.0.0")
]
ModelContextProtocol.ServerInfo {
name = "Darklang MCP Server";
version = "1.0.0"
}

let result =
Json.Object [
("protocolVersion", Json.String "2025-06-18");
("capabilities", serverCapabilities);
("serverInfo", serverInfo)
]
let initializeResult =
ModelContextProtocol.LifeCycle.InitializeRequest.InitializeResult.InitializeResult {
protocolVersion = ModelContextProtocol.protocolVersion;
serverInfo = serverInfo;
capabilities = serverCapabilities;
instructions = Stdlib.Option.Option.None
}

// Convert to JSON using the typed approach
let resultJson = ModelContextProtocol.LifeCycle.InitializeRequest.InitializeResult.toJson initializeResult

// Send the response
sendSuccessResponse (Stdlib.Option.Option.Some requestId) result
sendSuccessResponse (Stdlib.Option.Option.Some requestId) resultJson

// Return initialized state with all capabilities loaded
let state = initialState ()
Expand Down
59 changes: 39 additions & 20 deletions packages/darklang/languageTools/mcp-server/promptHandlers.dark
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Original file line number Diff line number Diff line change
Expand Up @@ -15,28 +15,47 @@ let handleListPromptsRequest
log "Handling prompts/list request"

let promptsList = state.prompts |> Stdlib.Dict.values
let result = Json.Object [
("prompts", Json.Array (promptsList |> Stdlib.List.map (fun prompt ->
Json.Object [
("name", Json.String prompt.name);
("description", Stdlib.Option.mapWithDefault prompt.description Json.Null (fun s -> Json.String s));
("arguments",
match prompt.arguments with
| Some args ->
Json.Array (args |> Stdlib.List.map (fun arg ->
Json.Object [
("name", Json.String arg.name);
("description", Stdlib.Option.mapWithDefault arg.description Json.Null (fun s -> Json.String s));
("required", Stdlib.Option.mapWithDefault arg.required Json.Null (fun b -> Json.Bool b))
]))
| None -> Json.Array []

log "A"

// Convert internal prompt format to MCP PromptDescription
let mcpPrompts = promptsList |> Stdlib.List.map (fun prompt ->
let mcpArguments =
match prompt.arguments with
| Some args ->
let convertedArgs = args |> Stdlib.List.map (fun arg ->
ModelContextProtocol.Prompts.PromptArgument.PromptArgument {
name = arg.name;
description = arg.description;
required = arg.required
}
)
]
)));
("nextCursor", Json.String "")
]
Stdlib.Option.Option.Some convertedArgs
| None -> Stdlib.Option.Option.None

ModelContextProtocol.Prompts.PromptDescription.PromptDescription {
name = prompt.name;
description = prompt.description;
arguments = mcpArguments
}
)
log "B"

let listResult =
ModelContextProtocol.Prompts.ListPromptsResponse.ListPromptsResult {
prompts = mcpPrompts;
nextCursor = Stdlib.Option.Option.None
}

log "C"
Builtin.debug "c" listResult


let resultJson = ModelContextProtocol.Prompts.ListPromptsResponse.toJson listResult

log "D"

sendSuccessResponse (Stdlib.Option.Option.Some requestId) result
sendSuccessResponse (Stdlib.Option.Option.Some requestId) resultJson
state

/// Handle a prompts/get request
Expand Down
30 changes: 18 additions & 12 deletions packages/darklang/languageTools/mcp-server/resourceHandlers.dark
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Original file line number Diff line number Diff line change
Expand Up @@ -17,19 +17,25 @@ let handleListResourcesRequest

let resourcesList = state.resources |> Stdlib.Dict.values

let response = Json.Object [
("resources", Json.Array (resourcesList |> Stdlib.List.map (fun resource ->
Json.Object [
("uri", Json.String resource.uri);
("name", Json.String resource.name);
("description", Stdlib.Option.mapWithDefault resource.description Json.Null (fun s -> Json.String s));
("mimeType", Stdlib.Option.mapWithDefault resource.mimeType Json.Null (fun s -> Json.String s))
]
)));
("nextCursor", Json.String "")
]
// Convert internal resource format to MCP ResourceDescription
let mcpResources = resourcesList |> Stdlib.List.map (fun resource ->
ModelContextProtocol.Resources.ListResourcesResponse.ResourceDescription {
uri = resource.uri;
name = resource.name;
description = resource.description;
mimeType = resource.mimeType
}
)

let listResponse =
ModelContextProtocol.Resources.ListResourcesResponse.ListResourcesResponse {
resources = mcpResources;
nextCursor = Stdlib.Option.Option.None
}

let responseJson = ModelContextProtocol.Resources.ListResourcesResponse.toJson listResponse

sendSuccessResponse (Stdlib.Option.Option.Some requestId) response
sendSuccessResponse (Stdlib.Option.Option.Some requestId) responseJson
state

/// Handle a resources/read request
Expand Down
12 changes: 2 additions & 10 deletions packages/darklang/languageTools/mcp-server/tools/searchFunctions.dark
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Original file line number Diff line number Diff line change
Expand Up @@ -54,16 +54,8 @@ let handleToolCall (args: Json) : Json =
| _ -> ""
| _ -> ""

// In a real implementation, this would search actual functions
let results = [
"Stdlib.List.map - Transform each element of a list";
"Stdlib.String.split - Split a string by delimiter";
"Stdlib.Dict.get - Get a value from a dictionary";
"Builtin.printLine - Print a line to stdout"
]

let resultsText =
$"Search results for '{query}':\n{Stdlib.String.join results "\n"}"
// Simple hardcoded results for now
let resultsText = $"Found 4 functions matching '{query}'"

(ModelContextProtocol.Tools.CallToolResponse.CallToolResult {
content = [
Expand Down
20 changes: 6 additions & 14 deletions packages/darklang/modelContextProtocol/common.dark
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Original file line number Diff line number Diff line change
Expand Up @@ -115,8 +115,7 @@ type GetPromptResult =

/// Prompt capabilities
type PromptCapabilities =
{ supportsPromptListing: Bool
listChanged: Stdlib.Option.Option<Bool> }
{ listChanged: Stdlib.Option.Option<Bool> }

/// Server information
type ServerInfo =
Expand All @@ -128,26 +127,19 @@ type ServerCapabilities =
{ resources: Stdlib.Option.Option<ResourceCapabilities>
tools: Stdlib.Option.Option<ToolCapabilities>
prompts: Stdlib.Option.Option<PromptCapabilities>
logging: Stdlib.Option.Option<LoggingCapabilities>
completion: Stdlib.Option.Option<CompletionCapabilities> }
logging: Stdlib.Option.Option<Json>
completions: Stdlib.Option.Option<Json>
experimental: Stdlib.Option.Option<Dict<Json>> }

/// Resource capabilities
type ResourceCapabilities =
{ supportsResourceListing: Bool
supportsResourceTemplates: Bool }
{ listChanged: Stdlib.Option.Option<Bool>
subscribe: Stdlib.Option.Option<Bool> }

/// Tool capabilities
type ToolCapabilities =
{ listChanged: Stdlib.Option.Option<Bool> }

/// Logging capabilities
type LoggingCapabilities =
{ level: Stdlib.Option.Option<LoggingLevel> }

/// Completion capabilities
type CompletionCapabilities =
{ supportsCompletion: Bool }

/// Error codes for the Model Context Protocol
module ErrorCodes =
let parseError = -32700L
Expand Down
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