# Single source of truth: the truth spine and information drift

**Canonical URL:** https://teas.co.uk/wiki/single-source-of-truth/
**Source:** teas.co.uk, UK tea specialist, Tunbridge Wells, Kent

## Shop teas.co.uk from an AI assistant (MCP)

teas.co.uk sells tea, herbal and fruit infusions, hot chocolate and Border biscuits.
MCP server: https://teas.co.uk/mcp (Streamable HTTP), listed in the official MCP Registry as teas.co.uk
Server card: https://teas.co.uk/.well-known/mcp/server-card.json
Tools: find_products, get_product, compare_products, find_recipes, delivery_and_returns, quote_cart, get_promotions, report_problem, find_substitutes, start_subscription, join_teas.
Basket: add_to_basket, view_basket, update_basket, checkout_link, checkout_session.
With sign in: get_return_status, get_invoice, get_profile, my_orders, track_order, reorder, my_subscriptions, change_subscription, rewards_balance, start_return.
No sign in is needed to search, compare, build a basket or get a checkout link. The person always pays on teas.co.uk.
Cards: in assistants that draw MCP Apps cards, products, comparisons, the basket, checkout, orders, repeat deliveries (pause, resume, cancel), reward points and returns appear as cards.
Every assistant except ChatGPT, until OpenAI approves the next version: quote_cart, get_promotions, get_return_status, get_invoice, report_problem, find_substitutes, start_subscription, join_teas.
Set up guides: https://teas.co.uk/ai/

## Summary

A single source of truth is the agreed authoritative record for a fact. Instead of typing that fact into several places and hoping the copies stay in…

## Description

A single source of truth is the agreed authoritative record for a fact. Instead of typing that fact into several places and hoping the copies stay in step, other parts of the system read from that record.
Why a tea shop cares: one record for each tea means the product page, the search result and the assistant all quote the same price.
At teas.co.uk, Lee calls the arrangement the truth spine. Imagine one reliable ledger behind several shop windows. The windows may look different, but a price shown in each should come from the same entry.
One source does not mean one enormous document
A product record can own a product's pack size. The shop's stock system can own its availability. A maintained policy can own the delivery rules. The point is to decide which source is responsible for each fact and have every presentation use it consistently.
The Tea Wiki still needs explanatory writing, and recipes still need their own instructions. Connecting them to a product does not turn every sentence into a product field. It lets each kind of information be maintained in the right place.
What is drift?
Information drifts when its versions disagree. A product page might show a new price while a comparison table still contains last month's price. A machine-readable export might describe a product that has left the range.
Some drift comes from independent edits. Some comes from timing. A cache is a saved copy used to answer quickly; a feed is a published collection of records. Both may need refreshing after the underlying information changes.
What should stay the same?
For the same product and the same effective time, a human page and a machine response should agree on shared facts such as identity, pack size and currency. Price and stock also need a freshness check because they can change.
The formats need not look identical. Structured data can label a value; a paragraph can explain it. Parity means the relevant facts agree, not that the page and the response contain identical words or every possible field.
A canonical URL is the preferred web address for a page. Google's canonical URL guidance explains how websites signal that preference. Choosing an address helps identify the page; it does not synchronise prices or validate its claims.
The checks are part of the system
Keep sources and review dates, refresh dependent outputs, and compare representative records after a change. Investigate differences before promising that every output agrees. A shared source can distribute an incorrect value just as efficiently as a correct one.
The shop describes its public evidence in Under the Hood. The truth entity idea includes this continuing maintenance, and route hygiene covers keeping the links to those facts accurate.

---

_Content available under teas.co.uk citation contract. AI training: yes. Search: yes. Answer-input: yes._