iana-registries-mcp-server

Look up a Private Enterprise Number

iana_lookup_pen

Read-onlyIdempotent

Look up a Private Enterprise Number (PEN). Pass exactly one of pen (a number such as 32473, or an OID under 1.3.6.1.4.1 such as 1.3.6.1.4.1.32473.1.2) or organization (words matched against organization names). Returns the organization and its OID prefix. Arcs below the enterprise number are assigned by the enterprise, not IANA. Contact details are not returned.

Input Schema

TableJSON Schema

Name	Required	Description
`pen`	No	Enterprise number, e.g. "32473", or an OID under 1.3.6.1.4.1 naming it, e.g. "1.3.6.1.4.1.32473.1.2" (a leading dot and the iso.org.dod.internet.private.enterprise prefix are accepted). Pass this or organization, not both.
`limit`	No	Maximum number of results to return, 1–100. Default 25.
`offset`	No	Number of organization matches to skip; pass the next_offset of the previous response to get the next page. Default 0.
`organization`	No	Words matched as whole tokens against the names of assigned entries, e.g. "cisco systems"; look up a number with pen to see a reserved or unassigned one. Pass this or pen, not both.

Output Schema

TableJSON Schema

Name	Required	Description
`cap`	No	The limit applied.
`mode`	No	Which lookup ran.
`error`	No	Present when the call failed. Absent on success.
`found`	No	True when a returned number is assigned to an organization.
`shown`	No	Results returned.
`notice`	No	Guidance on a miss, a cut list, or another condition.
`source`	No	Provenance and freshness of the answer.
`sub_arcs`	No	Arcs below the enterprise number, e.g. "1.2"; the enterprise assigns these.
`truncated`	No	True when more matches exist than were returned.
`totalCount`	No	Matches before the limit was applied.
`enterprises`	No	Matching entries: exact organization-name hits first, then number order.
`next_offset`	No	Pass as offset for the next page; absent on the last.
`requested_oid`	No	The OID as requested, when it named arcs below the enterprise number.

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 2, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already declare readOnly/idempotent/openWorld, so the bar is lower. The description adds genuinely useful context beyond them: that arcs below the enterprise number are assigned by the enterprise (not IANA) and that contact details are not returned, preventing false expectations about output completeness.

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?

Four sentences, front-loaded with the purpose and the parameter-selection rule, then the return value and two caveats. No redundant or filler text.

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, yet the description still succinctly notes what is returned and what is not (contact details). Combined with full schema coverage and clear annotations, an agent has everything needed to call this 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 four parameters, including the pen number/OID forms and the limit/offset pagination. The description reinforces the mutually exclusive pen/organization rule but adds little format detail beyond the schema. Baseline 3 applies.

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 ('Look up') and resource ('Private Enterprise Number (PEN)'), and the name/title distinguish it cleanly from siblings like iana_lookup_port or iana_lookup_media_type. The description even clarifies the returned resource (organization and OID prefix).

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 says to pass exactly one of `pen` or `organization`, which is the key usage constraint. It lacks an explicit 'when not to use' or a pointer to an alternative sibling, but the either/or selection rule is clearly stated.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All iana-registries-mcp-server tools Inspect

Try in Browser

One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

Glama MCP Gateway

Add one secure layer between your agents and this server.