FactGrid (Renamed to FactReason)

Package upgrade advisory

factreason_package_upgrade_advisory

Read-onlyIdempotent

Compare two exact published npm or PyPI versions and return publisher-declared registry metadata changes, including yanks, exports, module format, runtime floors, peers, and licences, with before/after evidence. Set responseFormat="compact" for tokenizer-measured context savings; the backward-compatible default is "full". This is a read-only metered lookup; misses are never billed and every API key carries one-off trial credit. Use it for package metadata; use factreason_api_breaking_changes for a third-party HTTP API, and consult changelogs for behavioural changes.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`to`	Yes	Exact target version, e.g. "5.0.0"
`from`	Yes	Exact currently installed version, e.g. "4.1.2"
`name`	Yes	Exact package name, e.g. "chalk" or "urllib3"
`apiKey`	No	Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.
`registry`	Yes	Registry containing both package versions
`responseFormat`	No	Use compact to remove repeated prose and fields while retaining evidence; full preserves the legacy response contract	full

Output Schema

TableJSON Schema

Name	Required	Description	Default
`found`	No
`scope`	No
`billed`	No
`message`	No
`toVersion`	No
`advisories`	No
`fromVersion`	No
`packageName`	No
`tokenMetrics`	No
`advisoryCount`	No
`breakingCount`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 4, 2026

addedInput schema / properties / apiKey

Added value: +{
+  "description": "Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.",
+  "maxLength": 128,
+  "minLength": 1,
+  "type": "string"
+}

Changed3 schema fields changedAug 17, 2026

addedInput schema / properties / responseFormat

Added value: +{
+  "default": "full",
+  "description": "Use compact to remove repeated prose and fields while retaining evidence; full preserves the legacy response contract",
+  "enum": [
+    "full",
+    "compact"
+  ],
+  "type": "string"
+}

addedOutput schema / properties / advisoryCount
```
Added value: +{
+  "type": "number"
+}
```

addedOutput schema / properties / tokenMetrics

Added value: +{
+  "additionalProperties": false,
+  "properties": {
+    "compactTokens": {
+      "type": "number"
+    },
+    "encoding": {
+      "const": "o200k_base",
+      "type": "string"
+    },
+    "fullTokens": {
+      "type": "number"
+    },
+    "reductionPct": {
+      "type": "number"
+    },
+    "savedTokens": {
+      "type": "number"
+    }
+  },
+  "type": "object"
+}

Changed9 schema fields changedAug 14, 2026

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

changedInput schema / properties / from / description

Previous value: -"Version currently installed, e.g. \"4.1.2\""New value: +"Exact currently installed version, e.g. \"4.1.2\""

addedInput schema / properties / from / minLength
```
Added value: +1
```

changedInput schema / properties / name / description

Previous value: -"Package name, e.g. \"chalk\", \"urllib3\""New value: +"Exact package name, e.g. \"chalk\" or \"urllib3\""

addedInput schema / properties / name / minLength
```
Added value: +1
```

changedInput schema / properties / registry / description

Previous value: -"Which registry the package is published on"New value: +"Registry containing both package versions"

changedInput schema / properties / to / description

Previous value: -"Version you intend to upgrade to, e.g. \"5.0.0\""New value: +"Exact target version, e.g. \"5.0.0\""

addedInput schema / properties / to / minLength
```
Added value: +1
```

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "properties": {
+    "advisories": {
+      "items": {
+        "additionalProperties": true,
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "billed": {
+      "type": "boolean"
+    },
+    "breakingCount": {
+      "type": "number"
+    },
+    "found": {
+      "type": "boolean"
+    },
+    "fromVersion": {
+      "type": "string"
+    },
+    "message": {
+      "type": "string"
+    },
+    "packageName": {
+      "type": "string"
+    },
+    "scope": {
+      "type": "string"
+    },
+    "toVersion": {
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

AddedAug 14, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), but the description adds genuinely new context: metered read-only billing, misses never billed, one-off trial credit per key, and that 'compact' is tokenizer-measured while 'full' preserves the legacy contract. It also scopes the answer to publisher-declared registry metadata, warning the agent off behavioural inference. It stops short of describing failure modes for an unpublished or nonexistent version pair.

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 purpose sentence, then format guidance, then billing terms, then sibling routing – each block earns its place. It is denser than ideal, packing four distinct concerns into one paragraph, but nothing is redundant.

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?

Output schema exists so return values need no explanation, annotations carry the safety profile, and the description supplies the remaining decision-critical pieces: sibling routing, response format tradeoff, and billing/auth context. An agent has everything needed to call 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 the schema already documents all six parameters including the responseFormat enum and the apiKey/Authorization interplay. The description's 'exact published versions' phrasing reinforces the from/to semantics and frames compact vs full as a context-cost tradeoff, but adds little syntax or format detail beyond what the schema states.

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 (two exact published npm or PyPI versions) and enumerates the exact output surface (yanks, exports, module format, runtime floors, peers, licences) with before/after evidence. It also explicitly distinguishes itself from the sibling factreason_api_breaking_changes, so an agent can route without opening either schema.

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?

Gives explicit when-to-use ('use it for package metadata'), names the competing sibling and the condition that selects it ('for a third-party HTTP API'), and adds a further exclusion ('consult changelogs for behavioural changes'). That is when/when-not/alternatives in one sentence.

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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