Creating a Query
All data reported to Tellor is associated with a unique queryId and a timestamp. When a user requests data using tip and when a reporter submits data using submitValue, they have to input both the queryId and queryData. The queryData tells reporters how to fulfill the data query, while also informing voters how to verify the data in a dispute. The queryId is defined as the keccak256 hash of the queryData field.
In order to query the Tellor oracle you'll need to first generate queryData and its hash, the queryId.
Getting a Query ID and Query Data
Use the tools below to generate a queryId and queryData:
If the existing Query Types don't fit your needs you'll need to define a new one.
Creating a new Query Type
To add a new data type to Tellor, you'll just need to define a new queryType. This is how you form a question so that Tellor reporters know exactly what data is being requested.
To create a new Query Type, or specification, for custom data you need from Tellor oracles, there are two options:
Register it using DataSpecs Registry Frontend site, using this as a this template.
Fill out this New Data Request Form and the Tellor Team will reach out to help put one together.
You'll need to determine three things: a unique queryType name, inputs, and outputs. So let's say you want a query for getting the price of any asset in any currency. In human-readable form, your question could look like this:
For example:
What is the price of BTC/USD?
You might formally define your query like this:
Name: SpotPrice
Inputs:
1. asset (string): Asset ID (e.g. btc)
2. currency (string): Selected currency (e.g. usd)
Outputs:
1. price (uint256)
- abi_type: ufixed256x18 (18 decimals of precision)
- packed: false
Next you need to incentivize reporters to fetch the answer to your question. Please see the Funding a Feed section to learn more.
Once Tellor reporters are submitting your new queryType on chain, you can retrieve your desired data with the help of UsingTellor, which is a helper contract that provides various Tellor data getters. You'll first put your question in queryData format, which means encoding your queryType name and arguments into bytes (see below). You'll then need to get a queryId, which is the bytes32 unique identifier for each Tellor data feed. The queryId is defined as the keccak256 hash of queryData. Once you know the queryId you'll be able to retrieve your data.
In Solidity, your contract can get data like this.
Example QueryData and QueryID
If you input btc and usd, respectively, the queryData would be:
0x00000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000080000000000000000000000000000000000000000000000000000000000000000953706f745072696365000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000c0000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000003627463000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000037573640000000000000000000000000000000000000000000000000000000000
and the queryId would be
0xa6f013ee236804827b77696d350e9f0ac3e879328f2a3021d473a0b778ad78ac
Next Steps
Feel free to start building a query now and integrating it into your project. When you reach the later stages of building your project, add it to the dataSpecs Registry to so that data reporters know how to fulfill your query. Please see the next section on how to fund a feed.
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