fourzerotwo

Search data APIs

search_apis

Read-onlyIdempotent

Find the right data endpoint for a task. Searches 500+ endpoints (UK legislation, Companies House, property prices, sanctions lists, vehicle tax, weather, earthquakes, arXiv/PubMed/Crossref papers, IP geolocation, GB electricity, ONS/World Bank/ECB economics, and more) by keyword and returns each match's tool name, parameters, price and free_tier. Always free to call. Next step: pass a returned tool name to call_api.

Input Schema

Name	Required	Description
`limit`	No	Maximum results (default 20).
`query`	No	Keywords describing the data you need; every word must match. Examples: "postcode", "sanctions screen", "sold prices", "earthquake", "bank holiday".
`category`	No	Optional category filter, e.g. "legal", "property", "finance", "research", "energy", "network". See list_apis for all categories.

Output Schema

Name	Required	Description	Default
`total`	Yes
`results`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed5 schema fields changedOct 11, 2026

addedInput schema / additionalProperties
```
Added value: +false
```

addedInput schema / properties / category

Added value: +{
+  "description": "Optional category filter, e.g. \"legal\", \"property\", \"finance\", \"research\", \"energy\", \"network\". See list_apis for all categories.",
+  "type": "string"
+}

addedInput schema / properties / limit

Added value: +{
+  "default": 20,
+  "description": "Maximum results (default 20).",
+  "maximum": 50,
+  "minimum": 1,
+  "type": "integer"
+}

changedInput schema / properties / query / description

Previous value: -"Keywords, e.g. \"probate\" or \"postcode\""New value: +"Keywords describing the data you need; every word must match. Examples: \"postcode\", \"sanctions screen\", \"sold prices\", \"earthquake\", \"bank holiday\"."

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "results": {
+      "items": {
+        "properties": {
+          "api": {
+            "type": "string"
+          },
+          "category": {
+            "type": "string"
+          },
+          "description": {
+            "type": "string"
+          },
+          "endpoint": {
+            "type": "string"
+          },
+          "free_tier": {
+            "enum": [
+              "free",
+              "sample",
+              null
+            ],
+            "type": [
+              "string",
+              "null"
+            ]
+          },
+          "params": {
+            "type": "array"
+          },
+          "price_usd": {
+            "type": "string"
+          },
+          "tool": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "tool",
+          "api",
+          "endpoint",
+          "price_usd"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "total": {
+      "type": "integer"
+    }
+  },
+  "required": [
+    "total",
+    "results"
+  ],
+  "type": "object"
+}

First observedOct 11, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already carry the read-only/idempotent/open-world safety profile, yet the description still adds material context: 'Always free to call' (cost/auth expectation) and the shape of each result. It does not discuss result limits or how partial keyword matches are ranked, but the added cost and return-shape context is genuinely useful beyond the annotations.

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

Conciseness4/5

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

Front-loaded with the core action and next step, with no filler sentences. The long parenthetical catalogue of domains is verbose but earns its place by helping the agent judge coverage.

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?

An output schema exists, so return values need not be spelled out, yet the description still names the key returned fields. Between the description and schema, an agent has everything needed to search, interpret results, and know the follow-up call.

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 query, limit and category are already documented in the schema. The description reinforces the keyword-search behavior but adds no syntax, format or matching-rule detail beyond what the schema states (e.g. it doesn't restate the 'every word must match' semantics or the limit cap).

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?

States a specific verb and resource ('Find the right data endpoint... Searches 500+ endpoints... by keyword') and enumerates the covered domains, making it unmistakable against siblings call_api and list_apis. The description also specifies exactly what each match returns (tool name, parameters, price, free_tier).

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

Usage Guidelines4/5

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

Gives clear sequencing guidance with 'Next step: pass a returned tool name to call_api', which routes the agent after the search. It does not, however, say when to prefer list_apis (e.g. browsing by category) over keyword search, leaving that comparison to inference.

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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