browser-compat-mcp-server

Browsercompat Search Features

browsercompat_search_features

Read-onlyIdempotent

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.

Input Schema

TableJSON Schema

Name	Required	Description
`group`	No	Restrict results to features in one web-features group or any group nested under it, for example "selectors" or "css". Keys with no web-features mapping never match. Call browsercompat_list_reference with topic groups for valid ids.
`limit`	No	Maximum results to return, from 1 to 50.
`query`	Yes	Plain-language name, keyword, or code notation, for example "container query", "fromAsync", "Array.prototype.at", "display: grid", or "<dialog>".
`offset`	No	Number of ranked matches to skip before returning results, for paging past limit. Pass the nextOffset from the previous response.
`baseline`	No	Restrict results to one Baseline state.
`snapshot`	No	Restrict results to features in one ECMAScript snapshot, for example "ecmascript-2023". Call browsercompat_list_reference with topic snapshots for valid ids.
`namespace`	No	Restrict results to one top-level browser-compat-data namespace.

Output Schema

TableJSON Schema

Name	Required	Description
`cap`	No	The limit that was applied.
`error`	No	Present when the call failed. Absent on success.
`shown`	No	Number of results on this page.
`results`	No	Ranked matches, best first. An empty array is a successful search with no hits.
`truncated`	No	True when more matches remain past this page.
`nextOffset`	No	The offset of the next page. Present only while matches remain past this page.
`totalCount`	No	Matches across every page, before offset and limit apply.
`data_version`	No	Vintage of each bundled dataset behind this answer.
`offsetNotice`	No	Why a page came back empty although the search matched.
`noMatchNotice`	No	How to broaden a search that matched nothing.
`appliedFilters`	No	Filters the server applied to this search.

Schema Changelog

Changes observed during successful MCP inspections.

Changed15 schema fields changedSep 22, 2026

addedInput schema / properties / group

Added value: +{
+  "description": "Restrict results to features in one web-features group or any group nested under it, for example \"selectors\" or \"css\". Keys with no web-features mapping never match. Call browsercompat_list_reference with topic groups for valid ids.",
+  "maxLength": 100,
+  "minLength": 1,
+  "type": "string"
+}

addedInput schema / properties / offset

Added value: +{
+  "default": 0,
+  "description": "Number of ranked matches to skip before returning results, for paging past limit. Pass the nextOffset from the previous response.",
+  "maximum": 9007199254740991,
+  "minimum": 0,
+  "type": "integer"
+}

changedInput schema / properties / query / description

Previous value: -"Plain-language name or keyword, for example \"container query\" or \"fromAsync\"."New value: +"Plain-language name, keyword, or code notation, for example \"container query\", \"fromAsync\", \"Array.prototype.at\", \"display: grid\", or \"<dialog>\"."

addedInput schema / properties / snapshot

Added value: +{
+  "description": "Restrict results to features in one ECMAScript snapshot, for example \"ecmascript-2023\". Call browsercompat_list_reference with topic snapshots for valid ids.",
+  "maxLength": 100,
+  "minLength": 1,
+  "type": "string"
+}

addedOutput schema / properties / appliedFilters / properties / group

Added value: +{
+  "description": "web-features group filter the search applied, nested groups included.",
+  "type": "string"
+}

addedOutput schema / properties / appliedFilters / properties / snapshot

Added value: +{
+  "description": "ECMAScript snapshot filter the search applied.",
+  "type": "string"
+}

changedOutput schema / properties / error / properties / data / properties / reason / description

Previous value: -"Machine-readable failure mode. Declared by this tool: `invalid_query`: query is whitespace-only after normalization, or normalizes to zero tokens. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `invalid_query`: query is whitespace-only after normalization, or normalizes to zero tokens. `unknown_group`: group names no web-features group in the bundled data. `unknown_snapshot`: snapshot names no ECMAScript snapshot in the bundled data. Other values are possible when a failure originates below the handler."

changedOutput schema / properties / error / properties / data / properties / reason / examples

Previous value: -[
-  "invalid_query"
-]New value: +[
+  "invalid_query",
+  "unknown_group",
+  "unknown_snapshot"
+]

addedOutput schema / properties / nextOffset

Added value: +{
+  "description": "The offset of the next page. Present only while matches remain past this page.",
+  "type": "number"
+}

addedOutput schema / properties / offsetNotice

Added value: +{
+  "description": "Why a page came back empty although the search matched.",
+  "type": "string"
+}

changedOutput schema / properties / results / items / properties / matched_on / description

Previous value: -"Which field matched the query, so the ranking can be inspected."New value: +"Which field matched the query, so the ranking can be inspected. path_suffix means the key ends in the dotted or property-value notation the query used, such as Element.animate or display: grid."

changedOutput schema / properties / results / items / properties / matched_on / enum

Previous value: -[
-  "bcd_key",
-  "baseline_id",
-  "name",
-  "caniuse_title",
-  "path_segment",
-  "description",
-  "path_tokens"
-]New value: +[
+  "bcd_key",
+  "baseline_id",
+  "name",
+  "caniuse_title",
+  "path_suffix",
+  "path_segment",
+  "description",
+  "path_tokens"
+]

changedOutput schema / properties / shown / description

Previous value: -"Number of results returned."New value: +"Number of results on this page."

changedOutput schema / properties / totalCount / description

Previous value: -"Matches before the display cap was applied."New value: +"Matches across every page, before offset and limit apply."

changedOutput schema / properties / truncated / description

Previous value: -"True when matches exceeded limit."New value: +"True when more matches remain past this page."

First observedSep 20, 2026

TDQS

A4.5/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint and idempotentHint, and the description adds genuinely useful behavioral context: matches are 'ranked', the result is a summary (not the full record), and the matching semantics include which field matched. It also discloses that keys with no web-features mapping never match. This goes beyond the annotation coverage without contradicting it.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three sentences, each earning its place: first scopes the search behavior, second states the return value and ranking, third routes to the follow-up tool. It is front-loaded and contains no filler or repetition of schema content.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 7-parameter search tool, the description covers purpose, scope, output format, and follow-up routing, while the schema and output schema handle parameter details and return structure. Sibling differentiation is addressed. Nothing an agent needs to call or interpret the result is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents every parameter thoroughly with examples and constraints. The description reinforces the query concept and introduces the cross-namespace scope, but does not need to add parameter-level meaning; baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb and resource: 'Find web features by plain name or keyword when the canonical key is unknown,' immediately distinguishing this tool from get_feature (which requires a known key). It scopes the feature domains explicitly and names the sibling to feed results into, so an agent can tell exactly what this tool does.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives a clear when-condition ('when the canonical key is unknown') and routes follow-up usage ('Feed a result key into browsercompat_get_feature for the full record'). It also points to browsercompat_list_reference in the schema for valid group/snapshot ids, explicitly guiding the agent away from guessing invalid parameters.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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