RealWorldAPIs

Compare APIs

compare_apis

Read-onlyIdempotent

Compare 2–8 already-known APIs side by side using canonical catalog fields plus capability-graph summary fields such as verified capability count, physical consequences, approval relevance and irreversibility. Use get_api for the full decision profile of one API and search_capabilities for capability-level filtering. No missing value is inferred and Unknown remains Unknown.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`apis`	Yes	Required list of 2–8 API slugs or names. Exact matches are preferred; unique partial matches are accepted. Unresolved identifiers are reported separately, and the call fails if fewer than two records resolve.
`fields`	No	Optional fields to compare. The default includes core catalog fields plus verified capability count, physical-consequence count, approval-relevant count, irreversible/high-consequence count and the decision-profile URL.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`name`	Yes
`fields`	Yes
`method`	Yes
`records`	Yes
`unresolved`	Yes
`evidence_policy`	Yes
`capability_graph`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedSep 30, 2026

changedInput schema / properties / fields / description

Previous value: -"Optional fields to compare. If omitted or empty, the tool uses the default core fields: provider, category, capabilities, agent_capabilities, auth_methods, openapi, mcp, a2a, x402, llms_txt, agent_readiness_score, public_documentation, authentication_verified and agent_actionable."New value: +"Optional fields to compare. The default includes core catalog fields plus verified capability count, physical-consequence count, approval-relevant count, irreversible/high-consequence count and the decision-profile URL."

changedInput schema / properties / fields / items / enum

Previous value: -[
-  "provider",
-  "category",
-  "description",
-  "capabilities",
-  "agent_capabilities",
-  "auth_methods",
-  "openapi",
-  "mcp",
-  "a2a",
-  "x402",
-  "llms_txt",
-  "agent_readiness_score",
-  "public_documentation",
-  "authentication_verified",
-  "agent_actionable",
-  "website",
-  "docs_url"
-]New value: +[
+  "provider",
+  "category",
+  "description",
+  "capabilities",
+  "agent_capabilities",
+  "auth_methods",
+  "openapi",
+  "mcp",
+  "a2a",
+  "x402",
+  "llms_txt",
+  "agent_readiness_score",
+  "public_documentation",
+  "authentication_verified",
+  "agent_actionable",
+  "website",
+  "docs_url",
+  "verified_capability_count",
+  "information_only_count",
+  "physical_consequence_count",
+  "irreversible_high_consequence_count",
+  "approval_relevant_count",
+  "capability_profile_url"
+]

addedOutput schema / properties / capability_graph
```
Added value: +{
+  "type": "string"
+}
```

Changed4 schema fields changedSep 27, 2026

changedInput schema / properties / apis / description

Previous value: -"API slugs or names."New value: +"Required list of 2–8 API slugs or names. Exact matches are preferred; unique partial matches are accepted. Unresolved identifiers are reported separately, and the call fails if fewer than two records resolve."

addedInput schema / properties / fields / description

Added value: +"Optional fields to compare. If omitted or empty, the tool uses the default core fields: provider, category, capabilities, agent_capabilities, auth_methods, openapi, mcp, a2a, x402, llms_txt, agent_readiness_score, public_documentation, authentication_verified and agent_actionable."

addedInput schema / properties / fields / uniqueItems
```
Added value: +true
```

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": false,
+  "properties": {
+    "evidence_policy": {
+      "type": "string"
+    },
+    "fields": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "method": {
+      "type": "string"
+    },
+    "name": {
+      "type": "string"
+    },
+    "records": {
+      "items": {
+        "additionalProperties": false,
+        "properties": {
+          "name": {
+            "type": "string"
+          },
+          "slug": {
+            "type": "string"
+          },
+          "values": {
+            "additionalProperties": true,
+            "type": "object"
+          }
+        },
+        "required": [
+          "slug",
+          "name",
+          "values"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "unresolved": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    }
+  },
+  "required": [
+    "name",
+    "method",
+    "fields",
+    "records",
+    "unresolved",
+    "evidence_policy"
+  ],
+  "type": "object"
+}

AddedSep 26, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already cover read-only, idempotent, non-destructive and non-open-world behavior, so the bar is lower. The description still adds useful data-handling semantics ('No missing value is inferred and Unknown remains Unknown'), which is real behavioral context an agent cannot get from 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?

Three tight sentences, front-loaded with the core comparison scope before the routing hints and data-semantics caveat. Nothing is wasteful, though the field enumeration slightly overlaps 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?

An output schema exists, so return values need not be explained, and annotations carry the safety profile. Combined with the description's purpose, sibling routing and unknown-value semantics, an agent has everything needed to invoke it correctly.

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 both parameters are fully documented in the schema, including the 2–8 limit, partial-match behavior and failure condition. The description's mention of 'canonical catalog fields plus capability-graph summary fields' largely restates what the fields schema already enumerates, so 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?

States a specific verb (compare) and resource (APIs) with an explicit scope of 2–8 already-known APIs and names the fields used for comparison. It also distinguishes itself from get_api and search_capabilities by naming them, so an agent can route correctly without opening schemas.

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?

Explicitly routes single-API deep dives to get_api and capability-level filtering to search_capabilities, which is clear alternative guidance. It stops short of stating when NOT to use it versus siblings like search_apis or find_api_for_task, so it is strong but not fully exhaustive.

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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