How-to guide · WebMCP adapter · v0.18.35

Call a WebMCP site's tools without a per-site adapter.

Ghostget's bundled webmcp adapter reads the public WebMCP Registry: sites that publish navigator.modelContext tools appear there with live-checked schemas. Search the registry, inspect one domain, and call tools declared read-only — all without an account, API key, or provider setup.

This guide describes v0.18.35. Registry content drifts between checks; the examples below return current results when you run them. The snapshot behind this site lists 1,802 domains as of 2026-09-23T07:17:21.268Z.

Find a site

sites.search lists registered domains. All inputs are optional: query matches names and tool descriptions, tag filters by registry tag (devtools, saas, ecommerce, and others), sort orders by popular, newest, or tools, and limit/cursor page through results.

ghostget webmcp sites.search --input '{"query":"docs"}' --json
ghostget webmcp sites.search --input '{"tag":"devtools","limit":10}' --json

Each result carries the domain, site name, tool count, read-only count, tags, and a nextCursor for paging.

Inspect one site's tools

sites.get returns the domain's current tools exactly as the registry last checked them: name, description, input schema, annotations, and the page URL the tool binds to.

ghostget webmcp sites.get --input '{"domain":"developers.cloudflare.com"}' --json

Read the readOnlyHint annotation per tool before planning a call. An unlisted domain fails closed with a structured provider error — the registry has no record to answer with.

Call a read-only tool

tools.call invokes one listed tool through the registry's headless executor. Pass the domain, the exact tool name from sites.get, and the tool input as a JSON object literal string matching its schema.

ghostget webmcp tools.call --input '{
  "domain": "developers.cloudflare.com",
  "tool": "search",
  "input": "{\"query\":\"workers\"}"
}' --json

The registry executes the tool on the target domain in a fresh headless page and returns the site's response. Ghostget bounds the request, validates the envelope, and returns the site output as untrusted content inside the receipt.

Limits

Only readOnlyHint tools can be invoked. A site may list mutating tools — purchases, writes, follows — that stay inspectable but cannot be called through the registry. Ghostget does not try to call around the gate.

Results are the site's own words. WebMCP tool output is untrusted third-party content returned verbatim in the receipt. Treat it like a page capture, not a verified fact.

Schemas move with the site. The registry re-checks domains continuously; a tool that appeared yesterday can rename its inputs today. Re-run sites.get rather than caching a schema, and let the structured provider error surface drift instead of retrying blindly.

This is the public discovery lane. Bundled adapters still own named services with accounts, previews, and mutation receipts. Use webmcp for the long tail; use a bundled adapter when the service has one.