Pounds, meet your assistant.

Connect once

Add a remote MCP server in your assistant with these settings:

The server is hosted by pound.one and free to use. There is nothing to install or run locally. All three tools are read-only: they calculate results from public data.

Your assistant needs remote MCP support. Use the server URL above in its connection settings; the address of this guide is for reading.

ChatGPT

1. In Settings, open Security and login and enable Developer mode.
2. Open Plugins, select +, and add https://pound.one/mcp. Name the connection pound.one, complete the details, and choose no authentication if asked.
3. Find pound.one in your personal plugins and select + to install it.
4. Start a Work chat. Type @, select pound.one, and ask a question.

See the official OpenAI connection guide for the current steps.

Codex

Run this command in your terminal:

codex mcp add pound-one --url https://pound.one/mcp

Start a fresh Codex session and use /mcp to check the connection. Then ask Codex to use pound.one. See the official Codex MCP guide.

A few things to ask

• “Use pound.one to work out what £30,000 in 2000 is worth today using CPI. Include the source and calculation link.”
• “What gross salary would give me £3,000 a month after tax in England?”
• “Put £1bn beside NHS spending. Explain which budget the comparison uses.”

You can combine the tools: find the salary that keeps up with inflation, then calculate its take-home pay. All money inputs are in GBP. Income inputs are annual, so £3,000 a month becomes £36,000 a year.

The three tools

Your assistant discovers the full input schemas when it connects. These examples show the arguments it sends.

adjust_for_inflation

Compare purchasing power, with prices, houses and wages where available. Required: amount (£0.01 to £1 trillion) and from (a whole year from 1948 to 2026). Optional: to (another year, or "now", the default) and series ("rpi", the default, or "cpi"). RPI starts in 1948; CPI starts in 1988. Amounts are rounded to pence.

{
  "amount": 30000,
  "from": 2000,
  "to": "now",
  "series": "cpi"
}

calculate_take_home

Estimate employee income tax and National Insurance using 2026/27 rules. Required: amount (annual income in whole pounds, £1 to £1 billion) and region ("england", "wales" or "northern_ireland"). Optional: mode, either "gross" (salary to take-home, the default) or "net" (target take-home to salary).

For £3,000 a month after tax in England:

{
  "amount": 36000,
  "mode": "net",
  "region": "england"
}

Scotland is not supported. The estimate assumes a standard tax code and excludes pensions, student loans, benefits and other income. The income ranking uses historical HMRC taxpayer data; its year is included in the result.

compare_public_spending

See a sum as a share and equivalent duration of a stored 2025-26 annual budget. Required: amount (£0.01 to £1 quadrillion). Optional: budget, defaulting to "nhs". Available budgets: everything, nhs, pensions, welfare, interest, education, defence, borrowing, taxes, monarchy.

{
  "amount": 1000000000,
  "budget": "nhs"
}

The NHS comparison uses DHSC day-to-day spending, principally England, and excludes capital. Other budgets have their own scope. These are illustrative averages; they overlap and cannot be added together.

Sources, dates and result links

Each result includes the calculation, source links, data periods, assumptions and caveats. “Now” means the latest stored observation, not a live price. Inflation, houses and wages can have different observation dates. Shop-price estimates are marked, and spending figures have not been reverified against later revisions.

Ask your assistant to preserve those qualifications and include a result link. The url field is the canonical calculator page; shareUrl opens the same result with campaign tags so we can count visits from assistants. The card field is a shareable image. CPI links preserve the selected measure.

What we count

We count tool calls, successes, errors and response times. Tool arguments, results and error messages are not retained in MCP analytics. Ordinary access records include IP addresses, user agents, request paths and status codes; a request to a calculator page includes its amount in the path.

Share links carry campaign tags. The private usage dashboard shows metrics since the server started, and its counters reset on restart. No cookies are set by the MCP server.

Registry and API

Registry name: one.pound/pound-one. Look up pound.one in the MCP Registry or read the server manifest. You can connect directly with the URL above.

Building a website or script? The JSON API exposes the same calculators without an MCP client. Read how the calculations work for more detail on the data.