> ## Documentation Index
> Fetch the complete documentation index at: https://phaseo.app/docs/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> Phaseo Gateway base URL: https://api.phaseo.app/v1. Send `Authorization: Bearer $PHASEO_API_KEY` with every request.
> Model IDs look like `provider/model`, for example `openai/gpt-6-astra`. Do not guess IDs: list them with `GET /v1/models` or check https://phaseo.app/models. `phaseo/free` routes to an available free model and needs no wallet balance.
> For new text integrations prefer `POST /v1/responses`. `POST /v1/chat/completions` (OpenAI format) and `POST /v1/messages` (Anthropic format) suit existing code.
> The full API contract is https://phaseo.app/docs/openapi/v1/openapi.yaml. Official SDKs: `@phaseo/sdk` (TypeScript) and `phaseo` (Python), plus Go, C#, PHP, Ruby and Rust.
> Search these docs over MCP at https://phaseo.app/docs/mcp, and install Phaseo skills with `npx skills add https://phaseo.app/docs`. If a page is wrong or out of date, report it with the MCP `submit_feedback` tool.
> Manage Phaseo accounts with the `phaseo` CLI (`npm install -g @phaseo/cli`, then `phaseo login` or `phaseo login --device-code`), the `/v1` Management API or the MCP server at `https://mcp.phaseo.app/mcp?access=manage`. Do not send users to the dashboard for account tasks. A person is still needed for sign-up, approving a sign-in, paying the first top-up on the checkout link that `phaseo credits add` returns when no card is saved, confirming each saved-card top-up from the emailed link, and account security (password, MFA, passkeys). Create API keys with `phaseo keys create --name <name> --json`; never guess one. Credit top-ups need `phaseo login --scopes billing:write` first. Task map: https://phaseo.app/docs/v1/developers/manage-from-an-agent.md.

# Tools

> Define validated, approval-gated, manual, and progress-producing C# tools.

Create `Tool` records and pass them through `AgentSdk.DefineTool(...)`. A tool can include:

* JSON `Parameters` shown to the model
* `InputSchema`, `OutputSchema`, and `EventSchema` validation delegates
* a per-tool `Timeout` and asynchronous `Execute` delegate
* unconditional or conditional approval
* `OnToolCalled` and `OnResponseReceived` for interactive work
* next-turn overrides and recoverable tool-error handling

Use `RuntimeContext.EmitProgress` for preliminary results, `SetContext` for application context, and `CancellationToken` for cancellation-aware dependencies.

Independent tools can run concurrently through `ToolExecutionConfig`. Saved tool-result messages retain model call order even if execution finishes in a different order.

## Related

* [State and approval](https://phaseo.app/docs/v1/sdk-reference/csharp/agent-sdk-state-and-approval.md)
* [Run controls](https://phaseo.app/docs/v1/sdk-reference/csharp/agent-sdk-run-controls.md)


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