osv-advisory-mcp-server

Osv List Ecosystems

osv_list_ecosystems

Read-onlyIdempotent

Return the supported ecosystem identifier strings for osv_query_package and osv_query_batch: every ecosystem the OSV schema names that OSV.dev accepts at query time, plus GIT, as verified on 2026-09-24. Ecosystem strings are case-sensitive exact matches — passing "pypi" instead of "PyPI" returns an error from the API. Use this tool to discover valid ecosystem strings before querying, or to verify an ecosystem identifier from a lockfile format. The list is static and may lag ecosystems added after that date.

Input Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Output Schema

TableJSON Schema

Name	Required	Description
`note`	No	Advisory note about list currency and canonical source.
`error`	No	Present when the call failed. Absent on success.
`ecosystems`	No	Supported ecosystem identifier strings. These are case-sensitive exact matches required by the ecosystem parameter of osv_query_package and osv_query_batch.

Schema Changelog

Changes observed during successful MCP inspections.

Changed6 schema fields changedAug 25, 2026

changedInput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

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

changedOutput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

addedOutput schema / anyOf

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "ecosystems",
+      "note"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

addedOutput schema / properties / error

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode.",
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

removedOutput schema / required

Removed value: -[
-  "ecosystems",
-  "note"
-]

Changed1 schema field changedJun 30, 2026

changedOutput schema / properties / ecosystems / description

Previous value: -"Supported ecosystem identifier strings. These are case-sensitive exact matches required by the ecosystem parameter of osv_query and osv_query_batch."New value: +"Supported ecosystem identifier strings. These are case-sensitive exact matches required by the ecosystem parameter of osv_query_package and osv_query_batch."

First observedMay 31, 2026

TDQS

A4.7/5.0

Behavior4/5

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

Annotations already provide readOnlyHint=true and idempotentHint=true, so the description doesn't need to repeat that. The description adds valuable context: ecosystem strings are case-sensitive, and the list is static and may lag behind new ecosystems as of the verified date. This helps set expectations about the tool's currentness and potential error behavior, which is beyond what annotations convey.

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?

The description is concise but packed with useful information. It front-loads the purpose and then adds critical usage and caveat details in a logical sequence. Each sentence earns its place: purpose, case-sensitivity warning, usage guidance, and freshness caveat. No fluff or repetition.

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?

There is an output schema, so the description needn't detail the return format. The description covers everything an agent needs to use this tool correctly: what it returns, why it's useful, the case-sensitivity constraint, and the staleness caveat. Given the zero-parameter nature and strong annotations, this is complete.

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

Parameters4/5

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

The tool has zero parameters, and schema coverage is 100% (no properties). The description still adds meaning by explaining the output (a list of ecosystem identifier strings) and its significance, which is useful even without parameters. Since there are no parameters to describe, the baseline of 4 is appropriate as it provides context about the output and its use.

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 clearly states the tool's purpose: to return supported ecosystem identifier strings for querying OSV. It specifies the exact resource (ecosystem identifiers) and the action (list), and mentions its role in supporting two sibling tools. It distinguishes itself from siblings by focusing on discovery of valid identifiers rather than querying vulnerabilities.

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 explicitly tells when to use this tool: before querying (osv_query_package or osv_query_batch) to discover valid ecosystem strings, or to verify an identifier from a lockfile. It also mentions that passing incorrect case (e.g., 'pypi' vs 'PyPI') will cause an error, effectively guiding the agent to use this tool to avoid that. It implicitly differentiates from siblings by positioning this as a discovery/verification step.

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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