modelparams.dev
xAI API key 5 params

xAI Grok 4.20 0309 Reasoning parameters

These are the parameters modelparams.dev tracks for xAI Grok 4.20 0309 Reasoning. Each row gives the type, default, valid range or values, and the conditions that gate it. It's the same data the JSON API serves.

Parameter Type Default Description Condition
Length · 1 param
Max completion tokens
max_completion_tokens 		integer (1…+∞) — Upper bound for visible output tokens generated in the chat completion. —
Sampling · 3 params
Temperature
temperature 		number (0…2 step 0.1) 1 Controls randomness. Lower values make outputs more focused; higher values make them more varied. —
Top P
top_p 		number (0…1 step 0.01) 1 Controls nucleus sampling by limiting generation to tokens within the selected cumulative probability. —
Seed
seed 		integer — Optional seed used for decoding when reproducible sampling is desired. —
Output · 1 param
Response format
response_format.type 		enum (text | json_object | json_schema) "text" Controls whether the model returns text, JSON mode output, or structured JSON schema output. —
This model as JSON All xAI models Parameter glossary Full catalog

Other xAI models

Grok 4.20 0309 Non Reasoning Grok 4.20 Multi Agent 0309 Grok 4.3 Grok Build 0.1

How to use

Building with an AI agent? Hit Copy to grab this whole guide as Markdown and paste it in — or point your agent straight at /llms.txt.

modelparams.dev is an open, community-maintained catalog of LLM model parameters. Each entry shows the knobs you can turn — type, default, range, and the conditions that gate it.

The same model accessed via an API key and via a subscription usually exposes a different set of parameters. We list both as separate entries so the data stays honest.

Catalog API

The full catalog is static JSON, CORS-enabled, served from the edge.

curl https://modelparams.dev/api/v1/models.json

Each entry is keyed by provider/model for API-key variants; subscription variants append -subscription.

Single model

curl https://modelparams.dev/api/v1/models/anthropic/claude-opus-4-7.json
curl https://modelparams.dev/api/v1/models/anthropic/claude-opus-4-7-subscription.json

JSON Schema

Every entry validates against a JSON Schema you can use in your editor or pipeline. 

curl https://modelparams.dev/api/v1/schema.json

Add this header to any YAML you author for autocomplete in VS Code: 

# yaml-language-server: $schema=https://modelparams.dev/api/v1/schema.json

Logos

Provider logos are available at /assets/logos/{provider}.svg where {provider} is the provider slug. They use currentColor so they inherit your text color. 

curl https://modelparams.dev/assets/logos/anthropic.svg

Logos are sourced from the models.dev repo (MIT) and used under nominative fair use.

Contribute

The data lives in YAML under models/{provider}/{model}-{auth}.yaml in the GitHub repo. Open a PR; CI validates against the schema and rebuilds.

Edit on GitHub MIT licensed