Missio REST Client

A lightweight, OpenCollection compatible REST API client for VS Code.

Missio uses the OpenCollection standard, which is file based (and AI friendly). Collaboration is supported via Git and external secret providers.

Missio is a REST Client without an identity crisis

What Missio Is:

• A VSCode Extension
• A REST Client
• Local, Git Native

What Missio Is Not:

• A Standalone IDE
• A SAAS Platform
• Cloud Synced
• A Monthly Subscription
• Feature Complete vs Postman

Missio aims to use VSCode functionality whereever possible.

Git integration, Workspaces, Commands, are all provided by VSCode.

BYO Agentic Coding tools.

Please Note

Missio is still in alpha. Key missing features from Postman include:

• Scripting
• Websockets
• GraphQL

We aim to support these in the coming weeks.

Features

Collections & Requests

• OpenCollection v1.0.0 compatible (partially at least) — YAML-based collections, requests, folder, and environments
• Auto-detect collections — scans workspace for collection.yml / workspace.yml
• Custom editors — visual editors for requests, folders, and collections with native dirty indicators, Ctrl+S save, and undo/redo
• Tree view sidebar — browse collections, folders, and requests with inline actions
• CodeLens — send requests directly from YAML files
• Import from Postman — import Postman v2.0/v2.1 collections and environments
• Import requests — paste a cURL, wget, or raw HTTP request and import it directly into a collection

Request Editor

• Visual request builder — method selector, URL bar, headers, query params, body (raw, form-encoded, multipart)
• Send with Ctrl+Enter — keyboard shortcut to send requests
• Response viewer — formatted body (JSON, XML, HTML) with syntax highlighting, word wrap, line numbers, headers, status, timing, and size
• Response preview — PDF and image responses render inline with an option to open in browser
• Cancel requests — cancel in-flight requests from the command palette or UI
• Request timer — live elapsed time display while a request is in progress, with the previous response dimmed until the new one arrives
• Auto headers — Content-Type and Content-Length are calculated automatically and shown as read-only (override by specifying your own)
• Unresolved variable prompts — if any {{variables}} remain unresolved after interpolation, a modal prompts you to fill them in before sending
• Save examples — save response snapshots and load them later

Variables & Environments

• Environment management — switch between dev/staging/prod with {{variable}} interpolation
• Variable inheritance — Collection > Folder > Environment (each layer overrides the previous)
• Variable highlighting — source-colored overlays on all input fields (URL, headers, params, body, auth)
• Click-to-inspect — click any {{variable}} to see its resolved value, source, and actions
• Toggle resolved values — {{}} button shows actual resolved values in-place across all fields
• Autocomplete — type {{ to get variable suggestions with source labels
• .env file support — automatically loads .env files from collection directories

Authentication

• Auth types — None, Bearer Token, Basic Auth, API Key, OAuth 2.0
• Auth inheritance — Request > Folder > Collection (first non-inherit wins)
• OAuth 2.0 — client credentials, password, and authorization code (PKCE) flows with automatic token management
• Token status display — live token expiry countdown with Get Token / Refresh buttons in request, folder, and collection editors
• Token caching — tokens stored securely per collection, environment, and credentials
• Refresh on 4xx — helper button on 4xx responses to clear a stale OAuth token and retry

Folder Defaults

• Folder editor — configure folder-level auth, headers, and variables via folder.yml
• Folder inheritance — folder defaults apply to all requests in the folder
• New folders default to inherit — auth set to inherit by default

Collection Editor

• Visual collection editor — overview, auth, headers, variables, and environments tabs
• Environment editor — add, remove, rename environments with variable key-value editing
• Collection-level defaults — set default auth and headers for all requests

Secret Providers

• Azure Key Vault — fetch secrets at runtime via az cli (no SDK required)
• Collection-scoped config — secret providers defined in collection.yml, fully portable
• $secret syntax — reference secrets with {{$secret.providerName.secretName}} in any field
• Secret autocomplete — type {{$secret. to get provider and secret name suggestions
• On-demand reveal — click a secret variable to see its source, then click "Reveal Value" to fetch and display it
• Test connection — verify vault access and RBAC from the collection editor's Secrets tab

Secret Providers

Secret providers are configured per-collection in collection.yml. Secrets are resolved at runtime — no secret values are stored in files.

Azure Key Vault

Prerequisites: az login and RBAC access (Key Vault Secrets User) on the vault.

Add a provider to your collection:

config:
  secretProviders:
    - name: my-vault
      type: azure-keyvault
      url: "https://my-vault.vault.azure.net"

The vault URL supports variables — useful for per-environment vaults:

config:
  secretProviders:
    - name: kv
      type: azure-keyvault
      url: "https://{{vault_name}}.vault.azure.net"

Then reference secrets anywhere you'd use a variable:

http:
  auth:
    type: bearer
    token: "{{$secret.my-vault.api-key}}"

Secrets are resolved at send time and during OAuth2 token acquisition. The collection editor's Secrets tab lets you test connections and see available secret names.

Commands

Keyboard Shortcuts

OpenCollection Spec

This extension implements the OpenCollection v1.0.0 specification. All unknown/unsupported fields in YAML files are preserved on save (round-trip safe).

• Schema: https://schema.opencollection.com/json/draft-07/opencollection/v1.0.0
• Workspace schema: https://schema.opencollection.com/json/draft-07/opencollection-workspace/v1.0.0

License

MIT