This section explains the main concepts in Langtail. If you are new to LLMs or prompt development, start from this glossary to familiarize yourself with the terminology.

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API keys

API Keys used to authenticate to Langtail. Can be generated here or from Deployments tab.

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Assertion

To validate the outputs of your language models and prompts, Langtail provides three powerful assertion types: Text, Javascript and LLMs.

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Config

A set of different prompt parameters that will be used in the test.

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Deploy

Creates a deployment of the selected prompt version.

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Deployment

A prompt version that is available on the Langtail API.

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Environment

An alias to a deployment. For example, the production API URL stays the same but is served by different deployments over time.

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Log

A single execution of a deployment. This allows you to see some metadata, the request to Langtail, the request to the provider, and the response from the provider.

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Magic button ✨

Magic buttons are kind of an easter egg hidden all over a Langtail UI. This button will usually help you enhance your prompts, generate test cases, and do other useful stuff via LLM. Let us know how many you’ve found!

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Member

A user in Langtail.

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Message

A specific type of template that is only used in the playground and not deployed with the prompt version.

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Metric

Aggregated data about activity in the prompt or project.

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Model

A LLM model that will be used to run the prompt.

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Output

The result of running a single test case. Either Success or Fail.

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Parameter

A single setting for the prompt. For example, model or temperature.

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Playground

An interface to easily edit and run a prompt. You can add templates, messages, variables, tools, and modify parameters.

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Preview deployment

A specific environment called preview.

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Production deployment

A specific environment called production.

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Project

A collection of prompts. Also contains project-level API keys (shared across prompts) and an aggregated view of metrics and logs (from all prompts).

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Prompt

A collection of parameters, templates, messages, variables, and tools. Sent as a single request to the model.

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Prompt version

A single version of a prompt which includes everything except for the messages entered in the playground. A user can revert back to a version at any time.

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Provider

Company or organization that develops, trains, and offers access to the underlying language model, such as OpenAI (for GPT models), Google (for LaMDA), or Anthropic (for Claude).

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Provider key

API key used to authenticate to the provider .

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Response

The response from the provider.

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Staging

deployment A specific environment called staging.

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Template

A text string that is part of a prompt. Valid types are system, assistant, user, function, and tool.

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Test

A collection of configs, assertions and test cases. When run, each individual case is compared against every config and assertion and shows an output.

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Test case

A user message and/or variable values which are executed with the prompt version that is being tested. When run, it returns an output.

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Tool

A single custom function definition. Based on the user message, the provider can invoke this function to get external data or provide extra functionality.

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Variable

Text that can be inserted into a template and changed dynamically when run.

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Workspace

A collection of projects.

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Workspace settings

Settings for a workspace where you can manage members and provider keys.