api-spec-cli

CLI for AI agents to explore and call OpenAPI, GraphQL, and MCP APIs. Output is TOON by default — compact, parseable, token-efficient.

Install

npm install -g api-spec-cli

Works with Node.js 18+. No other dependencies.

# Or run without installing
npx api-spec-cli <command>

How It Works

Every command is stateless — you specify the spec source on each call. Two paths:

| Path | When to use | |---|---| | --spec <name> | Registered spec — auto-fetches and caches on first use | | Inline flags | Ad-hoc — no registration, fetched each call |

Register once, use everywhere

spec add petstore --openapi https://petstore3.swagger.io/api/v3/openapi.json \
  --base-url https://petstore3.swagger.io/api/v3 \
  --description "Petstore example"

spec add hashnode --graphql https://gql.hashnode.com --auth YOUR_TOKEN

spec add agno --mcp-http https://docs.agno.com/mcp --description "Agno docs"

spec add fs --mcp-stdio "npx -y @modelcontextprotocol/server-filesystem /tmp"

spec import ~/.cursor/mcp.json
spec import ~/Library/Application\ Support/Claude/claude_desktop_config.json

Registration is instant — does not connect. Connection happens on first list/show/call. Spec/tool catalogs are cached 30 minutes; identical call results (same path + params) are cached 1 minute. Files live in ~/spec-cli-config/cache/.

Or use inline (no registration)

spec list --openapi https://petstore3.swagger.io/api/v3/openapi.json
spec list --graphql https://gql.hashnode.com
spec list --mcp-http https://docs.agno.com/mcp
spec list --mcp-sse http://localhost:3000/sse
spec list --mcp-stdio "npx -y @modelcontextprotocol/server-filesystem /tmp"

Inline specs use the same file cache (keyed from URL/command), so listTools is not repeated on every call within TTL.

Discovery

Search across specs

grep searches operation/tool names and descriptions across all registered specs.

spec grep search                        # Substring match across all specs
spec grep "get*"                        # Glob: anything starting with "get"
spec grep "*list*"                      # Glob: anything containing "list"
spec grep search --spec agno            # Limit to one spec

Matches on name and description. Case-insensitive. Plain text = substring, */? = glob.

List all specs in the registry

spec specs                    # Compact: name, type, enabled
spec specs --compact false    # Full: includes source, config

List operations / tools

list is compact (IDs only) and returns the first 20 tools/operations by default. total is the full catalog size. Use --filter, spec grep, --limit, and --offset on large MCP servers instead of dumping hundreds of tools. --limit 0 prints the whole catalog.

spec list --spec agno                          # Registered spec (uses cache)
spec list --spec petstore --filter pet         # Search by keyword
spec list --spec petstore --tag pets           # OpenAPI: filter by tag
spec list --spec hashnode --tag mutation        # GraphQL: filter by kind
spec list --spec petstore --limit 10           # First 10 only
spec list --spec petstore --limit 10 --offset 10  # Next 10
spec list --spec datadog --limit 0             # All tools (prefer grep on large servers)
spec list --mcp-http https://docs.agno.com/mcp # Inline: no registration needed
spec specs --filter datadog                    # Find a registered server by name
spec grep metric --spec datadog                # Search 300+ MCP tools without dumping them
spec grep metric --spec datadog --limit 10 --offset 10

Compact output (--format json shown for readability):

{
  "type": "mcp",
  "total": 1,
  "showing": 1,
  "operations": [
    { "id": "search_agno", "description": "Search across the Agno knowledge base..." }
  ]
}

Use --compact false for full details including inputSchema for MCP tools.

Inspect one operation or tool

show gives you everything to make a call — params, body schema, response schemas, related types — in one call.

spec show --spec petstore getPetById           # OpenAPI: by operationId
spec show --spec petstore /pet/{petId}         # OpenAPI: by path
spec show --spec petstore "GET /pet/{petId}"   # OpenAPI: by method + path
spec show --spec hashnode publishPost          # GraphQL: by operation name
spec show --spec agno search_agno             # MCP: by tool name

MCP output includes the full inputSchema so you know exactly what arguments to pass.

Drill into types (OpenAPI/GraphQL only)

spec types --spec petstore                     # List all schema names
spec types --spec petstore Pet                 # Inspect one schema
spec types --spec hashnode PublishPostInput    # GraphQL input type

Calling APIs

# OpenAPI
spec call --spec petstore getPetById --var petId=1
spec call --spec petstore findPetsByStatus --query status=available
spec call --spec petstore addPet --data '{"name":"Rex","photoUrls":[]}'

# GraphQL (auto-generates query from schema)
spec call --spec hashnode me
spec call --spec hashnode publication --var host=blog.hashnode.dev

# MCP
spec call --spec agno search_agno --var query="how to create an agent"
spec call --spec agno search_agno --data '{"query":"agents"}'

# Read body from stdin (explicit --data -)
echo '{"query":"agents"}' | spec call --spec agno search_agno --data -
cat body.json | spec call --spec petstore addPet --data -

# Inline (no registration)
spec call --openapi https://petstore3.swagger.io/api/v3/openapi.json \
  getPetById --var petId=1 --base-url https://petstore3.swagger.io/api/v3

Per-call overrides

Flags passed at call time win over registry entry config, which wins over .spec-cli/config.json.

spec call --spec agno search_agno --var query="foo" --header X-Tenant=acme
spec call --spec petstore getPetById --var petId=1 --auth staging-token
spec list --spec petstore --base-url https://staging.api.example.com

Registry Management

spec remove <name>    # Delete entry and remove cache
spec enable <name>    # Re-enable a disabled spec
spec disable <name>   # Disable without removing
spec refresh <name>   # Force re-fetch and update cache

spec add is an upsert — re-adding an existing name overwrites the entry (and clears its stale cache), since there's no separate update command. The response includes "overwritten": true when an existing entry was replaced.

Usage Ranking

spec records which operations/tools you call so agents can surface the ones that matter:

spec list --spec petstore --top 5   # the 5 most-called operations first
spec usage                          # recorded usage across all specs
spec usage petstore                 # ranked operations for one spec

Counts are stored locally in ~/spec-cli-config/usage.json. --top applies after --filter/--tag and overrides --limit. Set SPEC_NO_USAGE=1 to disable tracking.

Policy

Deny rules run on spec call only. Any matching block wins. Missing files = allow. SPEC_NO_POLICY=1 skips checks.

| File | When to use | |---|---| | ~/spec-cli-config/policies/<spec>.json | Common path — rules for one registered server | | ~/spec-cli-config/policy.json | Rules that apply across servers (globs, regex, no --spec name) | | .spec-cli/policy.json | Project-local (--local) |

--policies-path overrides the per-spec folder (default ~/spec-cli-config/policies). A plain --spec k8s writes policies/k8s.json. A glob like --spec k8s* stays in the global file.

spec policy
spec policy add --id no-prod-restart --spec k8s --tool restart \
  --when pod_name.prefix=prod --message "cannot restart prod pods"
spec policy add --data '{"id":"no-deletes","tool":{"regex":"^delete_.*"},"message":"destructive tools blocked"}'
spec policy show no-prod-restart
spec policy remove no-prod-restart --spec k8s
spec policy add --local --id no-etc --tool write_* --when path.glob=/etc/* --message "no writes under /etc"

--when is key=glob or key.op=value. Operators: eq, prefix, suffix, glob, regex, in, exists. Dotted keys walk nested args (metadata.namespace.prefix=prod). Tool/spec strings use the same glob rules as --allow-tool (exact or *).

A blocked call exits non-zero:

error: blocked by policy: cannot restart prod pods
rule: no-prod-restart

Rules with spec only apply when the call uses --spec <name>. Inline --openapi / --mcp-http / --graphql calls have no spec name, so match on tool / when instead.

Secrets & Environment Overrides

Stored values can reference secrets without putting them in argv or the registry. All of these expand at call time:

• ${VAR} from the environment
• env:NAME — same as mcp2cli, the whole value is an env var
• file:/path/to/secret — file contents (trailing newline stripped)

spec add gh --mcp-http https://api.example.com/mcp --header "Authorization=Bearer ${GH_TOKEN}"
spec add gh --mcp-http https://api.example.com/mcp --auth env:GH_TOKEN
spec add gh --mcp-http https://api.example.com/mcp --oauth-client-secret file:/run/secrets/oauth
spec config set auth '${API_TOKEN}'

A .env file in the working directory is auto-loaded on startup (real environment variables take precedence; set SPEC_NO_DOTENV=1 to disable).

Two environment variables override a registered spec's connection per call — useful in CI:

SPEC_URL=https://staging.example.com/mcp spec call --spec gh some_tool   # override MCP/GraphQL endpoint
SPEC_HEADER_X_TENANT=acme spec list --spec gh                            # add/override a header

SPEC_HEADER_<NAME> maps underscores to dashes (SPEC_HEADER_X_TENANT → X-Tenant). Precedence: call-time flags > env override > registry entry > project config.

Agent Skill

Install a ready-made skill that teaches an agent the explore-then-call workflow:

spec skill install   # copy SKILL.md into ~/.claude/skills/api-spec-cli/
spec skill path      # print the bundled SKILL.md location

spec add options

spec add <name> --openapi <url-or-file>   [--base-url <url>] [--auth <token>] [--header k=v]
spec add <name> --graphql <url>            [--auth <token>] [--header k=v]
spec add <name> --mcp-http <url>           [--auth <token>] [--header k=v]
spec add <name> --mcp-sse <url>            [--auth <token>] [--header k=v]
spec add <name> --mcp-stdio "<cmd args>"   [--env KEY=VAL] [--cwd <path>]
                                           [--description <text>]  (all types)

All options are repeatable where it makes sense (--header, --env). --auth adds Authorization: Bearer <token> unless the header is already set.

Operation filtering works for all spec types — MCP, OpenAPI, and GraphQL:

# MCP: allow only read/list tools
spec add <name> --mcp-http <url> \
  --allow-tool "read_*" --allow-tool "list_*" \
  --disable-tool "delete_*"

# OpenAPI: allow only GET operations (by operationId)
spec add <name> --openapi <url> \
  --allow-tool "get*" --allow-tool "find*"

# GraphQL: allow specific operations by exact name
spec add <name> --graphql <url> \
  --allow-tool "me" --allow-tool "publication"

--allow-tool keeps only matching operations. --disable-tool removes matching operations (applied after allow). Both are repeatable.

Matching rules:

• Plain text → exact match (case-insensitive): "me" matches only me
• Glob patterns → anchored match: "get*" matches getPetById, "*post*" matches createPost

Use grep for search (substring) — --allow-tool / --disable-tool for precise whitelists (exact or glob).

OAuth / Authentication

MCP HTTP and SSE servers that require OAuth 2.1 are handled automatically. spec-cli detects the 401 on spec add and runs the flow before returning.

Two modes depending on whether the server supports Dynamic Client Registration (DCR):

• DCR-enabled servers (e.g. self-hosted with Cloudflare workers-oauth-provider, Stytch, Curity) — no flags needed, browser opens automatically
• Pre-registered-only servers (e.g. GitHub) — pass --oauth-client-id with your app's client ID

Interactive (browser) — default

# DCR-enabled server: fully automatic
spec add myserver --mcp-http https://...

# GitHub (no DCR) — create an OAuth App at github.com/settings/developers first
# Set callback URL to http://127.0.0.1:8090/callback
spec add github --mcp-http https://api.githubcopilot.com/mcp/ \
  --oauth-client-id <your-github-app-client-id> \
  --oauth-callback-port 8090

Headless / device flow

spec add myserver --mcp-http https://... --oauth-flow device
# Prints a URL to stderr — open in any browser to authorize

Machine / CI (client credentials)

spec add myserver --mcp-http https://... \
  --oauth-flow client_credentials \
  --oauth-client-id <id> --oauth-client-secret <secret>

Re-authenticate

spec auth myserver           # Re-run the OAuth flow
spec auth myserver --revoke  # Clear stored token only

Tokens are stored in ~/spec-cli-config/tokens/<name>.json — separate from the cache, not touched by spec refresh. Access tokens are refreshed automatically: when a stored token expires, the refresh token is used and the rotated tokens are persisted, so the next command picks them up without re-authenticating.

OAuth flags

| Flag | Description | | --- | --- | | --oauth-client-id <id> | Skip DCR — use a pre-registered OAuth app client ID | | --oauth-client-secret <secret> | Use client credentials flow (machine/CI) | | --oauth-callback-port <port> | Fixed callback port (required for apps with exact redirect URL match, e.g. GitHub) | | --oauth-flow device | Force device authorization flow (headless/SSH) | | --oauth-flow client_credentials | Machine/CI flow (requires client id + secret) |

Reuse a stored MCP OAuth access token on an OpenAPI or GraphQL call (only if the token audience matches):

spec call --spec petstore getPet --auth-from github-mcp

Config

Persistent config stored in .spec-cli/config.json (lowest priority — overridden by registry entry config and call-time flags).

spec config set baseUrl https://api.example.com
spec config set auth my-token                        # Auto-adds "Bearer " prefix
spec config set auth "Basic dXNlcjpwYXNz"            # Or explicit scheme
spec config set headers.X-API-Key abc123              # Custom header (dot notation)
spec config get
spec config unset auth

Validate

spec validate https://api.example.com/openapi.json
spec validate ./openapi.yaml

Reports broken $ref references, missing required fields, duplicate operationIds, invalid schema types, and more.

Output Format

TOON by default. Errors go to stderr as plain text (error: ...) with a non-zero exit code.

spec list --spec petstore                      # TOON (default)
spec list --spec petstore --format json        # pretty-printed JSON
spec show --spec petstore getPetById --format yaml
spec list --spec petstore --format text

toon (Token-Oriented Object Notation) is the most token-efficient format for tabular/list output — the best choice when feeding results back into a model. Pass --format json for pretty-printed JSON. Help and errors are always plain text.

If formatted stdout is over 30000 characters (same ballpark as agent harness tool-result limits), spec writes the full payload as JSON to ~/spec-cli-config/results/ and prints a stub with path so you can rg / read chunks instead of swallowing the blob. Override with --max-bytes or SPEC_MAX_STDOUT. --max-bytes 0 always prints.

cached: true
path: C:\Users\you\spec-cli-config\results\2026-08-30T22-16-03-123.json
bytes: 184320
hint: rg <pattern> <path>

Token Efficiency

• list returns only IDs by default — no schemas
• show resolves $ref compactly — nested refs show as names, not explosions
• types lets you inspect one schema at a time
• --limit / --offset paginate large APIs (list/grep default to 20)
• Oversized call/show/list output spills to ~/spec-cli-config/results/ instead of flooding context
• --filter and --tag narrow results before output

MCP Options

# Retry on connection failure (useful for stdio servers that take time to start)
MCP_MAX_RETRIES=3       # Attempts (default: 3)
MCP_RETRY_DELAY=1000    # Base delay in ms, doubles each attempt, capped at 5s (default: 1000)

# HTTP timeout for OpenAPI/GraphQL calls
SPEC_HTTP_TIMEOUT=30000 # ms (default: 30000)

# File cache (global, ~/spec-cli-config/cache/)
SPEC_NO_CACHE=1              # Disable meta + call cache
SPEC_META_CACHE_MS=1800000   # Tools/schema TTL (default 30m)
SPEC_CALL_CACHE_MS=60000     # Call result TTL (default 1m)

Stdio env vars support ${VAR} expansion from the host environment:

spec add fs --mcp-stdio "npx -y server /tmp" --env "TOKEN=${MY_SECRET}"

Storage

| Path | Purpose | |---|---| | ~/spec-cli-config/registry.json | Global named registry | | ~/spec-cli-config/cache/ | File cache: meta-* (30m tools/schema) and call-* (1m results). Expired files are deleted on the next command. | | ~/spec-cli-config/tokens/<name>.json | OAuth tokens per MCP entry | | ~/spec-cli-config/usage.json | Operation/tool call counts for --top and spec usage | | ~/spec-cli-config/results/ | Full JSON for stdout that exceeded SPEC_MAX_STDOUT | | ~/spec-cli-config/policy.json | Global call-blocking policy (rules across all servers) | | ~/spec-cli-config/policies/<name>.json | Per-spec policy file | | .spec-cli/config.json | Project-local config (baseUrl, auth, headers) | | .spec-cli/policy.json | Project-local policy rules (merged with global; any block wins) |

Planned

• MCP resources and prompts (spec resources / spec prompts)
• OAuth for OpenAPI and GraphQL (not just MCP)