> ## 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 If a page is wrong or out of date, report it with the MCP `submit_feedback` tool.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 --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. # Agent SDK Overview > Build local, resumable agent loops on top of Phaseo Gateway across the supported Agent SDK languages. Use the Phaseo Agent SDKs when your application needs more than one-shot generation: * multi-step tool loops * local runtime tools * gateway-backed model turns * resumable application-owned run state * exact-call approvals, human-in-the-loop tools, manual tools, and resumable continuation * runtime validation, progress-producing tools, and recoverable tool errors * streamed model output with replayable event consumers * dynamic turn configuration, composable stop conditions, and normalized usage/cost * model retries, tool timeouts, bounded tool concurrency, and lifecycle events * local Phaseo Devtools capture * consistent request routing across the same languages as the core client SDKs ## Supported languages The current Agent SDK language set matches the primary client SDK set exposed in Phaseo quickstart: * [TypeScript](https://phaseo.app/docs/v1/sdk-reference/typescript/agent-sdk.md) * [Python](https://phaseo.app/docs/v1/sdk-reference/python/agent-sdk.md) * [Go](https://phaseo.app/docs/v1/sdk-reference/go/agent-sdk.md) * [C#](https://phaseo.app/docs/v1/sdk-reference/csharp/agent-sdk.md) * [PHP](https://phaseo.app/docs/v1/sdk-reference/php/agent-sdk.md) * [Ruby](https://phaseo.app/docs/v1/sdk-reference/ruby/agent-sdk.md) * [Rust](https://phaseo.app/docs/v1/sdk-reference/rust/agent-sdk.md) Ask a coding agent to build a first agent with the Phaseo Agent SDK in your language. Build a small agent in this project with the Phaseo Agent SDK. 1\. Install the Phaseo skills: npx skills add [https://phaseo.app/docs](https://phaseo.app/docs) For TypeScript, follow the phaseo-agent-sdk-typescript skill. 2\. Read the Agent SDK page for this project's language at [https://phaseo.app/docs/v1/sdk-reference/agent-sdk/overview](https://phaseo.app/docs/v1/sdk-reference/agent-sdk/overview.md) and use only the APIs it documents. 3\. Define one agent with at most two local tools that fit \[AGENT TASK]. Keep the loop bounded with a step limit, and require approval for any tool that changes data. 4\. Use a server-side PHASEO\_API\_KEY and check the model ID with GET /v1/models before using it. 5\. Stream the agent's steps to the console so a run can be inspected. 6\. Run the agent once, then report what you verified and what you could not verify. ## Common model Each Agent SDK keeps the same runtime model: * define one agent * define zero or more local tools * create a gateway-backed model client * run a bounded loop over the `responses` API * inspect lifecycle events or a Devtools trace * persist the returned run and resume after a human decision TypeScript is the reference API design. Python, Go, C#, PHP, and Ruby expose the broader cross-language contract using language-native callbacks, concurrency, timeout, and cancellation primitives. Rust is a supported synchronous runtime with local and external tools, exact-ID approvals, human review, model retries, serializable run state, lifecycle callbacks, and usage aggregation. Java and C++ remain work in progress. > [!NOTE] > > The Rust Agent SDK is published as [`phaseo-agent`](https://crates.io/crates/phaseo-agent). It does not yet include streaming, async execution, concurrent local tools, runtime schema validation, or Devtools capture. ## Cross-language capability contract | Capability | TypeScript | Python | Go | C# | PHP | Ruby | Rust | | - | - | - | - | - | - | - | - | | Executable tools and recoverable tool errors | Yes | Yes | Yes | Yes | Yes | Yes | Synchronous | | Exact-ID approvals, HITL, and manual outputs | Yes | Yes | Yes | Yes | Yes | Yes | Yes | | Preliminary tool progress | Async generator | Iterator or callback | Callback | Callback | Callback | Callback | Not yet | | Model streaming and replayable consumers | Async iterable | Iterator | Channel | Async enumerable | Iterable | Enumerator | Not yet | | Composable stop conditions | Yes | Yes | Yes | Yes | Yes | Yes | Step limit | | Dynamic turns and mutable context | Yes | Yes | Yes | Yes | Yes | Yes | Per-run model, step limit, and context | | Application-owned persisted run state | Yes | Yes | Yes | Yes | Yes | Yes | Serializable `RunResult` | | Normalized usage and cost | Yes | Yes | Yes | Yes | Yes | Yes | Tokens; custom-client cost only in `0.1` | PHP and Ruby expose provider stream events through their normal synchronous iteration APIs. They do not require a hosted runtime or a background Phaseo service. ## Client SDK, Agent SDK, and API | Use | Choose | What it owns | | - | - | - | | One API request or full endpoint coverage | Client SDK | Generated API types and transport | | Tool-using, multi-step application logic | Agent SDK | Local loop, tools, checkpoints, review, events, and Devtools | | Custom transport or an unsupported language | Raw API | HTTP request and response handling | Agent SDK gateway adapters delegate model turns to the matching Client SDK. Languages with a `requestOptions` or equivalent hook can pass additional Responses API fields through while the Agent SDK continues to own `model`, `input`, `instructions`, and local function tools. The Rust `0.1` adapter currently sends the normalized agent fields without an additional request-options hook. ## Recipes The cookbook includes TypeScript workflows and language-specific starting points: * [Build a durable agent loop](https://phaseo.app/docs/v1/cookbook/agent-sdk-durable-loop.md) * [Research with agent-backed web search](https://phaseo.app/docs/v1/cookbook/agent-sdk-research-brief.md) * [Triage support with preset-driven agents](https://phaseo.app/docs/v1/cookbook/agent-sdk-support-triage.md) * [Review code with local runtime tools](https://phaseo.app/docs/v1/cookbook/agent-sdk-coding-review.md) * [Fan out local tools concurrently](https://phaseo.app/docs/v1/cookbook/agent-sdk-parallel-tools.md) This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.