Agent Margin Router

npm Package

npm_package

Read-only

npm package intelligence: latest version, license, repository, maintainers, dependency count, publish dates and weekly downloads – ideal for dependency vetting by coding agents. Pay per call with USDC or USDT on Base via x402. 3 free calls per wallet.

Input Schema

TableJSON Schema

Name	Required	Description
`name`	Yes	npm package name (scoped allowed, e.g. @scope/pkg).
`wallet`	No	Your EVM wallet address (0x...). Unlocks the free tier (3 free calls per wallet).
`api_key`	No	Optional AMR enterprise API key.
`x_payment`	No	Optional signed x402 payment payload (base64 JSON) for USDC/USDT on Base.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`name`	Yes
`token`	No	Token actually used for payment (USDC, USDT or FREE).	USDC
`source`	Yes
`license`	No
`npm_url`	Yes
`routing`	Yes	How the request was routed (provider, fallback, cache, latency).
`homepage`	No
`keywords`	No
`cost_usdc`	Yes	Price charged in stablecoin units (USDC/USDT 1:1); 0 on the free tier.
`created_at`	No
`deprecated`	No
`fetched_at`	No	UTC timestamp when the data was fetched.
`description`	No
`maintainers`	No
`dependencies`	No
`version_count`	No
`latest_version`	No
`repository_url`	No
`dependency_count`	No
`weekly_downloads`	No
`freshness_seconds`	Yes	Age of the underlying data in seconds (0 = fetched live).
`x_payment_response`	No	Base64-encoded x402 settlement receipt (mirrors the X-PAYMENT-RESPONSE header). Only present when the call was paid with `x_payment`.
`latest_published_at`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 15, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "description": "Response for ``POST /npm-package``.",
+  "properties": {
+    "cost_usdc": {
+      "description": "Price charged in stablecoin units (USDC/USDT 1:1); 0 on the free tier.",
+      "title": "Cost Usdc",
+      "type": "number"
+    },
+    "created_at": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "title": "Created At"
+    },
+    "dependencies": {
+      "additionalProperties": true,
+      "title": "Dependencies",
+      "type": "object"
+    },
+    "dependency_count": {
+      "default": 0,
+      "title": "Dependency Count",
+      "type": "integer"
+    },
+    "deprecated": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "title": "Deprecated"
+    },
+    "description": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "title": "Description"
+    },
+    "fetched_at": {
+      "description": "UTC timestamp when the data was fetched.",
+      "format": "date-time",
+      "title": "Fetched At",
+      "type": "string"
+    },
+    "freshness_seconds": {
+      "description": "Age of the underlying data in seconds (0 = fetched live).",
+      "title": "Freshness Seconds",
+      "type": "integer"
+    },
+    "homepage": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "title": "Homepage"
+    },
+    "keywords": {
+      "items": {
+        "type": "string"
+      },
+      "title": "Keywords",
+      "type": "array"
+    },
+    "latest_published_at": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "title": "Latest Published At"
+    },
+    "latest_version": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "title": "Latest Version"
+    },
+    "license": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "title": "License"
+    },
+    "maintainers": {
+      "items": {
+        "anyOf": [
+          {
+            "type": "string"
+          },
+          {
+            "type": "null"
+          }
+        ]
+      },
+      "title": "Maintainers",
+      "type": "array"
+    },
+    "name": {
+      "title": "Name",
+      "type": "string"
+    },
+    "npm_url": {
+      "title": "Npm Url",
+      "type": "string"
+    },
+    "repository_url": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "title": "Repository Url"
+    },
+    "routing": {
+      "description": "How the request was routed (provider, fallback, cache, latency).",
+      "properties": {
+        "cache_hit": {
+          "default": false,
+          "description": "True if the result was served from cache.",
+          "title": "Cache Hit",
+          "type": "boolean"
+        },
+        "fallback_used": {
+          "default": false,
+          "description": "True if the primary provider failed and a fallback served the result.",
+          "title": "Fallback Used",
+          "type": "boolean"
+        },
+        "latency_ms": {
+          "default": 0,
+          "description": "End-to-end routing latency in milliseconds.",
+          "title": "Latency Ms",
+          "type": "integer"
+        },
+        "provider": {
+          "description": "Name of the upstream provider that served the result.",
+          "title": "Provider",
+          "type": "string"
+        },
+        "providers_tried": {
+          "description": "Providers attempted, in order.",
+          "items": {
+            "type": "string"
+          },
+          "title": "Providers Tried",
+          "type": "array"
+        }
+      },
+      "required": [
+        "provider"
+      ],
+      "title": "RoutingMeta",
+      "type": "object"
+    },
+    "source": {
+      "title": "Source",
+      "type": "string"
+    },
+    "token": {
+      "default": "USDC",
+      "description": "Token actually used for payment (USDC, USDT or FREE).",
+      "title": "Token",
+      "type": "string"
+    },
+    "version_count": {
+      "default": 0,
+      "title": "Version Count",
+      "type": "integer"
+    },
+    "weekly_downloads": {
+      "anyOf": [
+        {
+          "type": "integer"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "title": "Weekly Downloads"
+    },
+    "x_payment_response": {
+      "description": "Base64-encoded x402 settlement receipt (mirrors the X-PAYMENT-RESPONSE header). Only present when the call was paid with `x_payment`.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "freshness_seconds",
+    "cost_usdc",
+    "routing",
+    "name",
+    "npm_url",
+    "source"
+  ],
+  "type": "object"
+}

AddedSep 13, 2026

TDQS

A3.9/5.0

Behavior4/5

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

The description adds meaningful behavioral context beyond annotations by disclosing the payment model: 'Pay per call with USDC or USDT on Base via x402' and the free-tier limit of 3 calls per wallet. The readOnlyHint and openWorldHint annotations already cover safety and dynamic results, so the description's extra cost-related transparency is valuable. No contradiction with annotations exists.

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?

The description is compact: two sentences, with the core value prop and returned fields front-loaded, followed by the payment model. The opening phrase 'npm package intelligence' somewhat echoes the tool name, but the rest of the first sentence earns its place by enumerating useful outputs and the target use case.

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

Completeness4/5

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

Given that an output schema exists and the input schema fully documents parameters, the description covers the remaining essentials: what data is returned, the intended use case, and the payment/free-tier requirement. Nothing critical appears missing for an agent deciding whether and how to call this tool, though the description could be slightly more explicit about alternatives.

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 input schema already documents every parameter. The description mentions the free-tier wallet behavior, but this is redundant with the 'wallet' parameter's schema description. No additional parameter-level meaning is supplied beyond what the schema already provides, so the baseline of 3 is appropriate.

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

Purpose4/5

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

The description clearly identifies the resource (npm packages) and enumerates the specific data returned: version, license, repository, maintainers, dependency count, publish dates, and weekly downloads. It differentiates from the sibling pypi_package by naming npm explicitly, but it lacks an explicit action verb like 'get' or 'fetch', relying on the noun phrase 'package intelligence' to imply retrieval.

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?

The description gives a clear use case: 'ideal for dependency vetting by coding agents.' This tells an agent when to invoke the tool, though it does not explicitly name alternatives or state when not to use it. The npm-versus-PyPI distinction is implied by the ecosystem label rather than stated as an exclusion.

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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