---
title: "Add AllRatesToday to a Google ADK Agent with MCP"
description: "A production upgrade for the Google Skills currency-agent lab: extend your ADK agent with the AllRatesToday MCP server for 150+ fiat currencies, historical rates, and multi-target lookups."
canonical: https://allratestoday.com/blog/google-adk-allratestoday-mcp-agent/
source: AllRatesToday (https://allratestoday.com/) — Markdown mirror of the page above; index of all pages at https://allratestoday.com/llms.txt
generated: 2026-10-12T10:31:56.720Z
---

![AI agent connected to financial data tools](https://images.pexels.com/photos/8438918/pexels-photo-8438918.jpeg?auto=compress&cs=tinysrgb&dpr=2&h=650&w=940)

If you finished the Google Skills lab *[Add Currency Tools to an Agent using MCP](https://www.skills.google/focuses/145033?parent=catalog&path=3545)*, you built a Google ADK agent that calls Coinbase for crypto prices. That's a clean introduction to the Model Context Protocol — but Coinbase only covers crypto. The moment you want USD → EUR, INR → LKR, or any of the 150+ fiat pairs your users actually transact in, you need a different tool.

This guide walks through extending (not replacing) that lab agent with the [`@allratestoday/mcp-server`](https://www.npmjs.com/package/@allratestoday/mcp-server). By the end, your ADK agent will answer "what is 1,250 GBP in Singapore dollars right now?" with a live mid-market rate.

## What you'll build

An ADK agent ([Agent Development Kit](https://google.github.io/adk-docs/)) with two MCP tool sources wired in:

- **Coinbase MCP** — for crypto prices (BTC, ETH, etc.), kept from the original lab.
- **AllRatesToday MCP** — for 150+ fiat currencies, historical rates, and multi-target lookups.

Gemini picks the right tool based on the user's question. Crypto question → Coinbase. Fiat question → AllRatesToday. No code changes required to switch between them.

## Prerequisites

- **Python 3.10+** with the ADK installed: `pip install google-adk`
- **Node.js 18+** — the AllRatesToday MCP server ships as an npm package; `npx` handles install on first run.
- **A free AllRatesToday API key.** [Register here](https://allratestoday.com/register/) — no credit card. The key looks like `art_live_xxxxx`.
- **A Google Cloud project** with Vertex AI enabled (same setup as the original lab).

## Why extend with AllRatesToday?

|  | Coinbase API | AllRatesToday |
| --- | --- | --- |
| Crypto pairs | Yes | No |
| Fiat currencies | Limited (USD-quoted) | 150+, any base, any target |
| Historical data | Spot trades | 1d / 7d / 30d / 1y series |
| Data source | Coinbase exchange | Tier-1 financial providers |
| Update frequency | Real-time | ~60 seconds |
| Auth | Public for spot | Free API key |

For agents that handle invoices, travel budgets, e-commerce conversions, or any cross-border money flow, fiat coverage is non-negotiable. The two MCP servers compose cleanly — you don't have to pick one.

## Step 1: Verify the lab agent runs

Open the project from the Google Skills lab and confirm it still works:

```
cd ~/currency-agent
adk web
```

The ADK web UI opens at `http://localhost:8000`. Ask *"What's the price of Bitcoin?"* — it should call the Coinbase MCP and return a number. Stop the server (`Ctrl+C`) before continuing.

## Step 2: Add the AllRatesToday MCP server

Open `agent.py` (the file the lab had you edit when adding the Coinbase tool). It looks roughly like this:

```
from google.adk.agents import LlmAgent
from google.adk.tools.mcp_tool.mcp_toolset import MCPToolset, StdioServerParameters

root_agent = LlmAgent(
    model="gemini-2.0-flash",
    name="currency_agent",
    description="Agent that answers questions about currency prices.",
    instruction="Use the tools available to look up prices and exchange rates.",
    tools=[
        MCPToolset(
            connection_params=StdioServerParameters(
                command="npx",
                args=["-y", "@coinbase/mcp"],
            ),
        ),
    ],
)
```

Add a second `MCPToolset` entry and tighten the instruction so Gemini knows which tool to pick:

```
import os
from google.adk.agents import LlmAgent
from google.adk.tools.mcp_tool.mcp_toolset import MCPToolset, StdioServerParameters

root_agent = LlmAgent(
    model="gemini-2.0-flash",
    name="currency_agent",
    description="Agent that answers questions about crypto and fiat currency prices.",
    instruction=(
        "Use the Coinbase tool for cryptocurrency prices (BTC, ETH, etc.). "
        "Use the AllRatesToday tools for fiat currency conversions, "
        "historical rates, and any non-crypto currency question. "
        "Always cite the rate value you used."
    ),
    tools=[
        # Crypto via Coinbase (kept from the original lab)
        MCPToolset(
            connection_params=StdioServerParameters(
                command="npx",
                args=["-y", "@coinbase/mcp"],
            ),
        ),
        # Fiat via AllRatesToday
        MCPToolset(
            connection_params=StdioServerParameters(
                command="npx",
                args=["-y", "@allratestoday/mcp-server"],
                env={
                    "ALLRATES_API_KEY": os.environ["ALLRATES_API_KEY"],
                },
            ),
        ),
    ],
)
```

Two things worth noting:

- The updated `instruction` is load-bearing. Without it, Gemini routinely calls Coinbase for euros and gets nothing useful. Telling the model which tool maps to which domain fixes most tool-routing problems.
- The `env` is passed explicitly to the subprocess. The ADK doesn't forward your shell environment to MCP servers by default.

## Step 3: Export your API key

In the same shell where you'll run `adk web`:

```
export ALLRATES_API_KEY="art_live_your_key_here"
```

For Cloud Shell or persistent setups, add it to `~/.bashrc` or a `.env` file in the agent directory (the ADK auto-loads `.env`).

## Step 4: Run the agent

```
adk web
```

The first start downloads `@allratestoday/mcp-server` via `npx`. Subsequent starts are instant. In the ADK web UI, the left panel should now show **two** MCP tool sources, with a combined total of 5–6 tools.

Try these prompts:

- *"What's the current USD to EUR exchange rate?"* → calls `get_exchange_rate`.
- *"Convert 1,250 GBP to Singapore dollars."* → `get_exchange_rate` + arithmetic.
- *"Show me the USD/JPY trend over the last 30 days."* → `get_historical_rates` with `period=30d`.
- *"Give me today's EUR rates against USD, GBP, and CHF."* → `get_rates_authenticated` with comma-separated targets.
- *"What's the price of Bitcoin right now?"* → still routes to Coinbase. Both worlds work.

## The four tools you just gained

| Tool | Inputs | What it returns |
| --- | --- | --- |
| `get_exchange_rate` | `source`, `target` | Live mid-market rate between two ISO 4217 codes. |
| `get_historical_rates` | `source`, `target`, `period` | Time series: 1d (hourly), 7d, 30d (daily), 1y (weekly). |
| `get_rates_authenticated` | `source`, `target` (csv), optional `time` or `group` | Multi-target rates in one call with optional date / aggregation. |
| `list_currencies` | — | All 150+ supported currencies with metadata. |

## Production considerations

A few things to think about before shipping the agent past the demo stage.

### 1. Rate limits

The free tier is enough for testing. For production agents that make several tool calls per user turn, check the [pricing page](https://allratestoday.com/#pricing) and set quota alerts in your dashboard.

### 2. Caching

Rates update every 60 seconds upstream. Wrapping your agent in a thin cache (e.g. Redis with 30–60 second TTL keyed on the currency pair) cuts API calls by an order of magnitude without changing user experience.

### 3. Deploying to Vertex AI Agent Engine

Once you push your ADK agent to Vertex AI, the subprocess that runs `npx @allratestoday/mcp-server` still needs Node.js in the container. The base ADK image includes it. If you use a custom image, install Node 18+ in your Dockerfile.

### 4. Logging tool calls

Enable ADK's built-in tracing (`adk web --trace`) to see exactly which tool each user turn invoked, with arguments and returned values. Useful when debugging why the agent picked Coinbase instead of AllRatesToday (almost always an `instruction` wording issue).

## What about calling the REST API directly?

You can skip MCP entirely and call our REST API from a custom [function tool](https://google.github.io/adk-docs/tools/function-tools/). The trade-off:

- **Direct REST:** one less subprocess, slightly faster cold start, but you write and maintain the tool schema yourself.
- **MCP:** drop-in, the tool definitions come from the server, and the same package works in Claude Code, Cursor, and Claude Desktop without any rewrite.

For most agents, MCP wins on reusability — the same server you wired into ADK can power your IDE assistant tomorrow.

## Common errors

### `ALLRATES_API_KEY is required` on startup

The MCP server refuses to start without a key. Check `echo $ALLRATES_API_KEY` in the same shell where you ran `adk web`. If empty, re-export it.

### Gemini calls Coinbase for "EUR to USD"

Tighten the `instruction` field to make the routing explicit (the snippet above already does this). You can also rename the toolsets to give Gemini a clearer hint.

### `command not found: npx`

Node.js isn't installed (or isn't on PATH). Run `node --version`; if missing, install Node 18+ from [nodejs.org](https://nodejs.org/).

## Next steps

1. [Get your free API key](https://allratestoday.com/register/) — takes 30 seconds.
2. Drop the `MCPToolset` block above into your lab agent.
3. Try the example prompts. Confirm fiat questions hit AllRatesToday and crypto questions hit Coinbase.
4. Open an issue on [the MCP repo](https://github.com/cahthuranag/mcp-server) if you hit anything unexpected.

## Ship an ADK agent with real fiat currency data

150+ currencies, mid-market rates updated every 60 seconds. Free tier, no credit card.

 [Get your free API key](https://allratestoday.com/register/)

## Related Articles

- [AllRatesToday MCP Server in Claude Code & Cursor](https://allratestoday.com/blog/allratestoday-mcp-server-claude-cursor/)
- [Introducing the AllRatesToday MCP Server](https://allratestoday.com/blog/new-allratestoday-mcp-server-for-ai/)
- [Best MCP Servers for Finance 2026](https://allratestoday.com/blog/best-mcp-servers-for-finance-2026/)
- [Exchange Rate APIs for AI Agents and LLMs](https://allratestoday.com/blog/exchange-rate-api-ai-agents-llm-2026/)