add-dispatch-tool

name	add-dispatch-tool
description	Add a new tool to the AI dispatch agent. Use when the user wants to give the agent a new capability (e.g., "add a tool that returns load board listings older than 24h"). Walks through the four files that must change and the silently load-bearing WriteTools step.

Add a Dispatch Tool

Adds a new tool that the AI dispatch agent can call. Tools are auto-discovered via DI: each tool is a class implementing IAiDispatchTool, registered in Registrar.cs, and described in AiDispatchToolRegistry.cs for the LLM.

Files that must change

1. src/Infrastructure/Logistics.Infrastructure.AI/Tools/{ToolName}Tool.cs — the tool implementation
2. src/Infrastructure/Logistics.Infrastructure.AI/Services/AiDispatchToolRegistry.cs — JSON schema + description for the LLM
3. src/Infrastructure/Logistics.Infrastructure.AI/Registrar.cs — DI registration
4. src/Infrastructure/Logistics.Infrastructure.AI/Services/AiDispatchDecisionProcessor.cs — only if write tool, add name to WriteTools HashSet
5. tests/Logistics.Infrastructure.AI.Tests/Tools/{ToolName}ToolTests.cs — unit test

Step-by-step

1. Decide read vs write

• Read tool: pure query — runs immediately in both Autonomous and HumanInTheLoop modes. Examples: get_unassigned_loads, check_hos_feasibility.
• Write tool: mutates state (assigns load, dispatches trip, books from load board). In HumanInTheLoop mode it creates a Suggested decision; in Autonomous mode it executes immediately.

If write tool, you must add the tool name to WriteTools HashSet in step 4 — missing this step breaks HumanInTheLoop approvals silently.

2. Create the tool class

Tools/{ToolName}Tool.cs. Tool names use snake_case. Pattern:

using System.Text.Json;
using System.Text.Json.Nodes;

namespace Logistics.Infrastructure.AI.Tools;

internal sealed class GetSomethingTool(ITenantUnitOfWork tenantUow) : IAiDispatchTool
{
    public string Name => "get_something";

    public async Task<string> ExecuteAsync(JsonNode input, CancellationToken ct)
    {
        // 1. Parse and validate input
        var someId = input["some_id"]?.GetValue<string>();
        if (string.IsNullOrEmpty(someId))
            return JsonSerializer.Serialize(new { error = "Missing some_id" });

        // 2. Do the work via tenantUow / mediator / domain services
        // Inject IMediator if you need to dispatch a command/query

        // 3. Return JSON string. Keep payloads compact — every byte costs LLM tokens.
        return JsonSerializer.Serialize(new { /* fields */ });
    }
}

Conventions:

• internal sealed class with primary-constructor DI
• Tool name in snake_case, matching Name property
• Always return JSON string, never throw — surface errors as { error = "..." }
• Inject the smallest dependency you need (ITenantUnitOfWork, IMediator, IGeocodingService, etc.) — tools are Scoped
• For write tools that map to existing commands, dispatch via IMediator.Send(new XCommand(...), ct)

3. Add the schema definition

In AiDispatchToolRegistry.cs, append to the Tools list. The JSON schema is what the LLM sees — descriptions matter:

new("get_something",
    "Returns X for Y. Include 1-2 sentences describing inputs, outputs, and when to call this vs alternatives.",
    BuildSchema(new JsonObject
    {
        ["type"] = "object",
        ["properties"] = new JsonObject
        {
            ["some_id"] = Prop("string", "GUID of the entity")
        },
        ["required"] = new JsonArray("some_id")
    })),

Group with other read tools or other write tools (look at the ── Read Tools ── / ── Write Tools ── comments).

4. Register in DI

In Registrar.cs, add to the AddAiDispatchInfrastructure method alongside the other tools:

services.AddScoped<IAiDispatchTool, GetSomethingTool>();

5. If write tool, register in WriteTools

In AiDispatchDecisionProcessor.cs, add the tool name to the WriteTools HashSet:

private static readonly HashSet<string> WriteTools =
[
    "assign_load_to_truck",
    "create_trip",
    "dispatch_trip",
    "book_loadboard_load",
    "get_something" // ← new write tool
];

Skip this step for read tools. Read tools always execute immediately.

6. Write a unit test

tests/Logistics.Infrastructure.AI.Tests/Tools/{ToolName}ToolTests.cs. Use NSubstitute and MockQueryable.NSubstitute for IQueryable-returning repositories. Pattern:

public class GetSomethingToolTests
{
    private readonly ITenantUnitOfWork tenantUow = Substitute.For<ITenantUnitOfWork>();
    private readonly GetSomethingTool sut;

    public GetSomethingToolTests() => sut = new GetSomethingTool(tenantUow);

    [Fact]
    public async Task ExecuteAsync_MissingId_ReturnsError()
    {
        var input = JsonNode.Parse("""{}""")!;
        var result = await sut.ExecuteAsync(input, CancellationToken.None);
        result.Should().Contain("\"error\"");
    }

    [Fact]
    public async Task ExecuteAsync_ValidInput_ReturnsExpectedFields() { /* ... */ }
}

Verification checklist

Before reporting done:

• Tool class created, implements IAiDispatchTool, name is snake_case
• Registered in Registrar.cs (otherwise DI won't find it and AiDispatchToolExecutor returns "Unknown tool")
• Added to AiDispatchToolRegistry.Tools list (otherwise the LLM never knows it exists)
• If write tool: added to AiDispatchDecisionProcessor.WriteTools HashSet
• Unit test added under tests/Logistics.Infrastructure.AI.Tests/Tools/
• dotnet build passes
• dotnet test --filter "{ToolName}ToolTests" passes

Common mistakes

• Missing WriteTools registration: Tool runs in Autonomous mode but is silently auto-executed in HumanInTheLoop instead of creating a Suggested decision.
• Throwing instead of returning {error}: The agent loop catches exceptions but the agent loses the context of what went wrong.
• Verbose tool names or descriptions: Every tool definition is sent on every API call — keep descriptions tight.
• Not registering in Registrar.cs: AiDispatchToolExecutor.toolMap is built from DI; an unregistered tool is invisible at runtime.

Related

• .claude/rules/backend/ai-agent.md — overall AI agent conventions
• docs/ai-dispatch.md — agent architecture
• feature-map.md → AI dispatch row