fcc-spectrum-mcp-server

List FCC ULS reference codes and coverage

fcc_spectrum_list_reference

Read-onlyIdempotent

Decode FCC ULS codes used by the other tools — radio service codes, station classes, license statuses, location types, antenna types, applicant types, amateur operator classes — or report coverage: which service groups this index holds, record counts, and when each was last updated. Works before the index is built. Station classes describe licensed categories, not actual on-air activity.

Input Schema

Name	Required	Description	Default
`topic`	Yes	What to list: a code vocabulary (radio_services, station_classes, license_statuses, location_types, antenna_types, applicant_types, operator_classes) or coverage, the index build state and loaded service groups.
`filter`	No	radio_services and station_classes only: keep entries whose code and label contain every token given, in any order (e.g. "700 public safety" or "FB2"). Case- and accent-insensitive; punctuation separates tokens. A nonblank filter must normalize to at least one ASCII letter or digit; blank means unset. Other topics disclose that filter was not applied.

Output Schema

Name	Required	Description
`error`	No	Present when the call failed. Absent on success.
`index`	No	Index build state; present for coverage.
`topic`	No	The topic answered.
`groups`	No	Every weekly service group this server can index, with whether it is loaded; present for coverage.
`notice`	No	Guidance when a filter matched nothing, was not applied, or the index is not built yet.
`entries`	No	Decoded codes, in code order; present for every topic except coverage.
`dataAsOf`	No	Creation time of the newest applied ULS file (ISO 8601); absent before the index is built.
`redactIndividuals`	No	True when individual licensees are redacted and excluded from name search; present for coverage.

Schema Changelog

Changes observed during successful MCP inspections.

Changed7 schema fields changedOct 13, 2026

changedInput schema / properties / filter / description

Previous value: -"Radio services only: keep entries whose code and label contain every word given, in any order (e.g. \"700 public safety\"). Case- and accent-insensitive."New value: +"radio_services and station_classes only: keep entries whose code and label contain every token given, in any order (e.g. \"700 public safety\" or \"FB2\"). Case- and accent-insensitive; punctuation separates tokens. A nonblank filter must normalize to at least one ASCII letter or digit; blank means unset. Other topics disclose that filter was not applied."

changedInput schema / properties / topic / description

Previous value: -"What to list: a code vocabulary (radio_services, license_statuses, location_types, antenna_types, applicant_types, operator_classes) or coverage, the index build state and loaded service groups."New value: +"What to list: a code vocabulary (radio_services, station_classes, license_statuses, location_types, antenna_types, applicant_types, operator_classes) or coverage, the index build state and loaded service groups."

changedInput schema / properties / topic / enum

Previous value: -[
-  "radio_services",
-  "license_statuses",
-  "location_types",
-  "antenna_types",
-  "applicant_types",
-  "operator_classes",
-  "coverage"
-]New value: +[
+  "radio_services",
+  "station_classes",
+  "license_statuses",
+  "location_types",
+  "antenna_types",
+  "applicant_types",
+  "operator_classes",
+  "coverage"
+]

changedOutput schema / properties / error / properties / data / properties / reason / description

Previous value: -"Machine-readable failure mode."New value: +"Machine-readable failure mode. Declared by this tool: `invalid_filter`: A nonblank filter on radio_services or station_classes normalizes to no searchable tokens. Other values are possible when a failure originates below the handler."

addedOutput schema / properties / error / properties / data / properties / reason / examples
```
Added value: +[
+  "invalid_filter"
+]
```

addedOutput schema / properties / index / properties / antennaCoverageIncomplete

Added value: +{
+  "description": "True when earlier decoding discarded unnumbered antenna records; searches remain available, but a complete weekly rebuild is needed.",
+  "type": "boolean"
+}

changedOutput schema / properties / topic / enum

Previous value: -[
-  "radio_services",
-  "license_statuses",
-  "location_types",
-  "antenna_types",
-  "applicant_types",
-  "operator_classes",
-  "coverage"
-]New value: +[
+  "radio_services",
+  "station_classes",
+  "license_statuses",
+  "location_types",
+  "antenna_types",
+  "applicant_types",
+  "operator_classes",
+  "coverage"
+]

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 cover read-only/idempotent/closed-world, so the description earns credit for going further: it discloses that the tool still functions before the index is built, and warns that station classes are licensed categories rather than actual on-air activity — a semantic caveat an agent would otherwise get wrong.

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?

Dense but front-loaded, leading with the decode purpose before the coverage alternative and the station-class caveat. No wasted sentences, though the long em-dash enumeration is slightly heavy.

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?

With an output schema present, return values need not be described, and annotations cover safety. The description covers both modes (decode vs coverage) and the key caveat; the only omission is an explicit statement of when to prefer this over fetching a license directly.

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?

Schema coverage is 100% (baseline 3), but the description adds real meaning beyond the schema: it spells out what "coverage" returns (service groups held, record counts, last-updated) and characterizes the vocabularies. It does not restate the filter's token-normalization rules, which the schema already handles.

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?

Specific verb+resource: decode FCC ULS code vocabularies or report index coverage. The enumeration of code families makes it immediately distinguishable from the fcc_spectrum_search_*/find_* siblings, which operate on records rather than reference vocabularies.

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?

"Decode FCC ULS codes used by the other tools" frames this as the lookup companion to the sibling search tools, and "Works before the index is built" gives a clear precondition context. No explicit when-not guidance, but the reference-vs-record distinction is unambiguous.

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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