# io.github.cyanheads/browser-compat-mcp-server

> Browser compatibility and Baseline status for any web feature — offline, from bundled MDN data.

- name: io.github.cyanheads/browser-compat-mcp-server
- version: 0.2.1
- connection class: R0 (autonomous)
- trust: 94/100
- quality: 79/100 (good)
- owner: not claimed
- descriptor: https://api.protogrid.dev/v1/servers/io.github.cyanheads%2Fbrowser-compat-mcp-server
- tools: https://api.protogrid.dev/v1/servers/io.github.cyanheads%2Fbrowser-compat-mcp-server/tools

**An agent can connect right now, no human step.** Remote endpoint, no authentication, reachable on the last probe.

## Connection (mcpServers)

```json
{
  "mcpServers": {
    "browser-compat-mcp-server": {
      "type": "http",
      "url": "https://browser-compat.caseyjhand.com/mcp"
    }
  }
}
```


## Trust

- hygiene: 100
- liveness: 100
- freshness: 100
- provenance: 80
- drivers: +repository +namespace-matches-repo +reachable +uptime-99% +updated-5d-ago
- Derived from observable signals (official registry feed and our own credential-free probes); no code audit performed.

## Quality 79/100 (good)

### protocol: 100 (weight 25)

- pass `protocol.modern`: supports 2026-07-28 (server/discover)
- pass `protocol.stateless`: answers without a session
- pass `protocol.transport`: streamable HTTP
- pass `protocol.list_ttl`: tool list is cacheable (ttlMs 3600000)

### authorization: n/a (weight 15)

- n/a `auth.prm`, `auth.as_metadata`, `auth.cimd`: no remote uses OAuth
- n/a `auth.secret_in_url`: no templated URL

### tool hygiene: 79 (weight 30)

- pass `tools.descriptions`: every tool has a description
- warn `tools.description_length`: 1 tools have descriptions over 1,024 characters, which crowds the context
- pass `tools.schemas`: every tool has an object input schema
- pass `tools.annotations`: 5 of 5 tools declare readOnlyHint or destructiveHint
- fail `tools.directory_hints`: no tool declares all four of readOnlyHint, destructiveHint, idempotentHint and openWorldHint; missing: browsercompat_get_feature (destructiveHint); browsercompat_check_baseline (destructiveHint); browsercompat_compare_support (destructiveHint); …
- pass `tools.token_cost`: about 2,967 tokens to load every tool
- pass `tools.api_dump`: tools are not a one-to-one API dump

### stability: 25 (weight 15)

- warn `stability.changes`: 7 tool changes in 30 days
- fail `stability.rug_pull`: 1 tools kept their name but changed most of their description in 30 days; review before trusting them

### dependencies: 100 (weight 15)

- pass `deps.known_vulns`: no known advisory in 94 resolved packages
- pass `deps.mcp_sdk_version`: @modelcontextprotocol/core 2.3.1, no known advisory
- pass `deps.resolvable`: @cyanheads/browser-compat-mcp-server@0.2.1, @cyanheads/browser-compat-mcp-server@0.2.1 resolved: 94 packages

- tools: 5, about 2,967 tokens to load them all
- tool set hash: 23f0d6cf62f90efe854b19bb6ca90f70
- tools last changed: 2026-10-16T04:00:52.770Z
- badge: [![protogrid quality](https://protogrid.dev/badge/io.github.cyanheads/browser-compat-mcp-server.svg)](https://protogrid.dev/servers/io.github.cyanheads/browser-compat-mcp-server)
- Checks run on what our credential-free, read-only probes observe; tools are never called and no code audit is performed.

### Tool changes

- 2026-10-16 `browsercompat_compare_support` changed (description, inputSchema, outputSchema)
  - before: Compute whether a set of web features clears an explicit browserslist target query. Every call evaluates the whole query: each feature gets a verdict, the count of failing targets, and its own evaluated and unevaluated target counts with the share of tracked traffic each covers. The target rows behind those numbers — which release each target maps to, which targets were not evaluated and why, and the failing and unevaluated targets of each feature — cover at most ten query targets per call; page through them with target_offset and target_limit, and the verdicts, coverage, and totals stay identical on every page. A target counts as evaluated only where compatibility data was read for it, so a feature clears only when every target in the query was evaluated and supports it, and is inconclusive otherwise — a query that includes a browser with no compatibility data, as "defaults" does, never clears.
  - after: Compute whether a set of web features clears an explicit browserslist target query. Compares up to 20 features per call; up to 100 may be sent, and entries past the 20th come back unevaluated in omitted_features for the next call. Every call evaluates the whole query: each feature gets a verdict, the count of failing targets, those targets grouped into runs of consecutive query targets per browser in failing_ranges, and its own evaluated and unevaluated target counts with the share of tracked traffic each covers. The target rows behind those numbers — which release each target maps to, which targets were not evaluated and why, and the failing and unevaluated targets of each feature, a failing row carrying the prefix, alternative name, or flag behind its verdict — cover at most ten query targets per call; page through them with target_offset and target_limit, and the verdicts, coverage, and totals stay identical on every page. A target counts as evaluated only where compatibility data was read for it, so a feature clears only when every target in the query was evaluated and supports it, and is inconclusive otherwise — a query that includes a browser with no compatibility data, as "defaults" does, never clears. A BCD key is judged on its own per-browser support. A web-features id spanning several keys, such as grid, is judged on the release web-features lists for the feature as a whole in each Baseline core browser, as support_source says; its other browsers are not evaluated.
- 2026-10-16 `browsercompat_search_features` changed (inputSchema, outputSchema)
- 2026-10-16 `browsercompat_check_baseline` changed (description, inputSchema, outputSchema)
  - before: Check whether web features are safe to ship: Baseline state and the date it crossed, the browser and version that limits support, whether the feature is deprecated or discouraged, and the share of tracked global traffic that requiring it would exclude. Accepts up to 20 BCD keys or web-features ids in one call.
  - after: Check whether web features are safe to ship: Baseline state and the date it crossed, the browser and version that limits support, whether the feature is deprecated or discouraged, and the share of tracked global traffic that requiring it would exclude. Evaluates up to 20 BCD keys or web-features ids per call; up to 100 may be sent, and entries past the 20th come back unevaluated in omitted_features for the next call.
- 2026-10-16 `browsercompat_get_feature` changed (description, inputSchema, outputSchema)
  - before: Get the compatibility record for one web feature: Baseline state and the date it crossed, deprecation and standards status, per-browser version added and removed with flags, vendor prefixes and partial-implementation notes, and the MDN and specification links. Accepts a BCD key such as css.selectors.has or a web-features id such as has; the response echoes which one it matched. An unresolved feature returns found: false with guidance rather than an error.
  - after: Get the compatibility record for one web feature: Baseline state and the date it crossed, deprecation and standards status, per-browser version added and removed with flags, vendor prefixes and partial-implementation notes — with every other support statement recorded for that browser, such as an earlier prefixed or flagged release, in other_statements — and the MDN and specification links. Accepts a BCD key such as css.selectors.has or a web-features id such as has; the response echoes which one it matched. A web-features id that spans several BCD keys, such as grid, returns web-features’ own feature-level release per Baseline core browser in feature_support and its compat_keys, 100 per page, in place of per-key fields. An unresolved feature returns found: false with guidance rather than an error.
- 2026-09-30 `browsercompat_compare_support` changed (description, inputSchema, outputSchema) **meaning changed**
  - before: Compute whether a set of web features clears an explicit browserslist target query. Returns a per-feature verdict, the target browser and version that fails, the share of tracked traffic the targets cover, and unchecked_targets for every resolved target browser with no compatibility data. A feature is never reported as clearing a target the server could not evaluate.
  - after: Compute whether a set of web features clears an explicit browserslist target query. Every call evaluates the whole query: each feature gets a verdict, the count of failing targets, and its own evaluated and unevaluated target counts with the share of tracked traffic each covers. The target rows behind those numbers — which release each target maps to, which targets were not evaluated and why, and the failing and unevaluated targets of each feature — cover at most ten query targets per call; page through them with target_offset and target_limit, and the verdicts, coverage, and totals stay identical on every page. A target counts as evaluated only where compatibility data was read for it, so a feature clears only when every target in the query was evaluated and supports it, and is inconclusive otherwise — a query that includes a browser with no compatibility data, as "defaults" does, never clears.
- 2026-09-30 `browsercompat_check_baseline` changed (inputSchema, outputSchema)
- 2026-09-30 `browsercompat_get_feature` changed (inputSchema, outputSchema)

Full history: https://api.protogrid.dev/v1/servers/io.github.cyanheads%2Fbrowser-compat-mcp-server/changes

## Dependencies

- npm @cyanheads/browser-compat-mcp-server@0.2.1: resolved, 46 dependencies, MCP SDK @modelcontextprotocol/core 2.3.1
- npm @cyanheads/browser-compat-mcp-server@0.2.1: resolved, 46 dependencies, MCP SDK @modelcontextprotocol/core 2.3.1

Dependency graphs from deps.dev; advisories from OSV.dev, including the GitHub Advisory Database and the PyPI Advisory Database; all CC BY 4.0.

## Remotes

- https://browser-compat.caseyjhand.com/mcp (streamable-http, auth none, reachable true, uptime30d 0.9915254)

## Packages

- npm @cyanheads/browser-compat-mcp-server@0.2.1
- npm @cyanheads/browser-compat-mcp-server@0.2.1

## Tools (5)

- `browsercompat_check_baseline`: Check whether web features are safe to ship: Baseline state and the date it crossed, the browser and version that limits support, whether the feature is deprecated or discouraged, and the share of tracked global traffic that requiring it would exclude. Evaluates up to 20 BCD keys or web-features ids per call; up to 100 may be sent, and entries past the 20th come back unevaluated in omitted_features for the next call.
- `browsercompat_compare_support`: Compute whether a set of web features clears an explicit browserslist target query. Compares up to 20 features per call; up to 100 may be sent, and entries past the 20th come back unevaluated in omitted_features for the next call. Every call evaluates the whole query: each feature gets a verdict, the count of failing targets, those targets grouped into runs of consecutive query targets per browser in failing_ranges, and its own evaluated and unevaluated target counts with the share of tracked traffic each covers. The target rows behind those numbers — which release each target maps to, which targets were not evaluated and why, and the failing and unevaluated targets of each feature, a failing row carrying the prefix, alternative name, or flag behind its verdict — cover at most ten query targets per call; page through them with target_offset and target_limit, and the verdicts, coverage, and totals stay identical on every page. A target counts as evaluated only where compatibility data was read for it, so a feature clears only when every target in the query was evaluated and supports it, and is inconclusive otherwise — a query that includes a browser with no compatibility data, as "defaults" does, never clears. A BCD key is judged on its own per-browser support. A web-features id spanning several keys, such as grid, is judged on the release web-features lists for the feature as a whole in each Baseline core browser, as support_source says; its other browsers are not evaluated.
- `browsercompat_get_feature`: Get the compatibility record for one web feature: Baseline state and the date it crossed, deprecation and standards status, per-browser version added and removed with flags, vendor prefixes and partial-implementation notes — with every other support statement recorded for that browser, such as an earlier prefixed or flagged release, in other_statements — and the MDN and specification links. Accepts a BCD key such as css.selectors.has or a web-features id such as has; the response echoes which one it matched. A web-features id that spans several BCD keys, such as grid, returns web-features’ own feature-level release per Baseline core browser in feature_support and its compat_keys, 100 per page, in place of per-key fields. An unresolved feature returns found: false with guidance rather than an error.
- `browsercompat_list_reference`: Enumerate the reference vocabulary this server uses: BCD namespaces, BCD browser ids, browserslist agent ids and their BCD counterparts, Baseline states, web-features groups, and ECMAScript snapshots. Use it to build valid inputs for the other tools and to see which target browsers can be evaluated.
- `browsercompat_search_features`: Find web features by plain name or keyword when the canonical key is unknown, across CSS, JavaScript, HTML, Web APIs, SVG, MathML, WebAssembly, and HTTP headers. Returns ranked matches with the BCD key, the web-features id, the Baseline state, a one-line support summary, and which field matched. Feed a result key into browsercompat_get_feature for the full record.