McpSource.ResourceTools

C# · package Toolnexus · SPEC §2 · McpResources.cs

public List<ITool> McpSource.ResourceTools();
// [0] list_mcp_resources { server? }       → "server uri — name (mimeType): description" per line
// [1] read_mcp_resource  { server, uri }   → the resource's text

Two read-only tools (Hints.ReadOnly = true) bound to the source’s connected servers. Opt-in: they are not added to a toolkit on their own; register them with ExtraTools. They stop working once the McpSource is disposed. A source with no connected server still returns both; they report that no server is connected. An unknown server or uri is an error result, not an exception.

When to use it

An MCP server exposes data as resources (files, records, docs) rather than tools, and you want the model to browse and read them itself.

Why this and not the alternative

Examples

1. The two tools, even with no server

using Toolnexus;

await using var src = await McpSource.LoadAsync("""{"mcp":{}}""");
var tools = src.ResourceTools();

if (string.Join(",", tools.Select(t => t.Name)) != "list_mcp_resources,read_mcp_resource") throw new Exception("names");
if (!tools.All(t => t.Hints!.ReadOnly)) throw new Exception("expected read-only hints");
Console.WriteLine($"ok: {string.Join(", ", tools.Select(t => t.Name))} (read-only)");

2. List and read a server’s resource

using Toolnexus;

// TOOLNEXUS_REPO is set by the docs test runner; in your own code use your server's path.
var repo = Environment.GetEnvironmentVariable("TOOLNEXUS_REPO") ?? ".";
var server = Path.Combine(repo, "examples", "mcp-progress-server.mjs");
var cfg = "{\"mcp\":{\"progress\":{\"command\":\"node\",\"args\":[" + System.Text.Json.JsonSerializer.Serialize(server) + "]}}}";

await using var src = await McpSource.LoadAsync(cfg);
var (list, read) = (src.ResourceTools()[0], src.ResourceTools()[1]);

var listed = await list.ExecuteAsync(new Dictionary<string, object?>());
var text = await read.ExecuteAsync(new Dictionary<string, object?> { ["server"] = "progress", ["uri"] = "fixture://hello" });
var missing = await read.ExecuteAsync(new Dictionary<string, object?> { ["server"] = "progress", ["uri"] = "fixture://nope" });

if (text.Output != "hello resource" || !missing.IsError) throw new Exception(text.Output);
Console.WriteLine($"ok: {listed.Output} → \"{text.Output}\"");

3. Hand them to the model through a toolkit

using Toolnexus;

var repo = Environment.GetEnvironmentVariable("TOOLNEXUS_REPO") ?? ".";
var server = Path.Combine(repo, "examples", "mcp-progress-server.mjs");
var cfg = "{\"mcp\":{\"progress\":{\"command\":\"node\",\"args\":[" + System.Text.Json.JsonSerializer.Serialize(server) + "]}}}";

await using var src = await McpSource.LoadAsync(cfg);
await using var tk = await Toolkit.CreateAsync(new Toolkit.Options { ExtraTools = src.ResourceTools() });

var r = await tk.ExecuteAsync("read_mcp_resource", new Dictionary<string, object?> { ["server"] = "progress", ["uri"] = "fixture://hello" });
if (r.Output != "hello resource") throw new Exception(r.Output);
Console.WriteLine($"ok: the toolkit offers {string.Join(", ", tk.Tools().Select(t => t.Name))}");