lookup_packageLook up every registry a package or repository is published to, via package URL (purl) or repository URL. Returns matching package records across all registries. Keyless.
| Name | Required | Description | Default |
|---|---|---|---|
| purl | No | A package URL, e.g. "pkg:npm/lodash" or "pkg:pypi/django". | |
| repository_url | No | A source repository URL, e.g. "https://github.com/facebook/react". |
Changes observed during successful MCP inspections.
Input schema / examplesAdded value: +[
+ {
+ "purl": "pkg:npm/lodash"
+ },
+ {
+ "repository_url": "https://github.com/facebook/react"
+ }
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, openWorldHint, idempotentHint, destructiveHint. The description adds 'Keyless' implying no auth needed, which is useful but minimal. No contradictions with annotations.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two sentences front-loaded with the main purpose, followed by a clarifying sentence and a one-word behavioral note. No wasted words.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Adequate for a simple tool: mentions both parameters and return type (records), but lacks detail on record structure since no output schema. Also unclear if both params can be omitted.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100% so parameters are already documented. Description merely restates that it uses purl or repository_url without adding new semantics beyond the schema.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states it looks up every registry a package or repository is published to via purl or repository URL. It distinguishes from siblings like get_package and list_registries by emphasizing cross-registry lookup.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description implies usage for finding registries for a given package but does not explicitly state when to use vs alternatives like scan_dependency or get_package. No exclusions or when-not-to-use guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.