# libofcongress-mcp-server MCP Server

Search LOC digital collections, Chronicling America newspapers (full OCR), and LC Subject Headings.

**Publisher claimed.** No tool list reported, and Pod has not connected to this server.

## Status

Pod has not dialled libofcongress-mcp-server yet, so everything on this page is what its publisher reported rather than what we observed. Registries describe servers; they do not connect to them. Until a check runs, treat the tool list below as a claim.

## Connect

Published as `@cyanheads/libofcongress-mcp-server` on npm. Runs locally.

## Known issues

**40 problems reported by people outside the maintainer team.** Issues filed by the project's own owners, members and collaborators are excluded — those are release checklists and internal refactors, not things that will go wrong for you. Showing 12.

### Most discussed

### bug(loc_get_item,loc_get_newspaper_page): internal LOC API URL with query params leaked in not-found error messages

Not-found errors from `libofcongress_get_item`, `libofcongress_get_newspaper_page`, and the `libofcongress://item/{item_id}` resource expose the full internal LOC API URL — including query parameters like `?fo=json&at=item,resources,related_items` — in `data.url`. The same leak occurs in `serviceUnavailable` errors when the LOC API returns an HTML body instead of JSON (rate-limited or maintenance page).

### Steps to reproduce

1. Call `libofcongress_get_item` with input: `{ "item_id": "TOTALLY_

[Read the thread](https://github.com/cyanheads/libofcongress-mcp-server/issues/1) · 2026-05-24 · closed · 6 comments

### bug(loc_get_item): format() truncates related_items at 5 without indicating truncation — parity gap with structuredContent

### Server version

0.1.0

### mcp-ts-core version

0.9.9

### Runtime

Node.js

### Runtime version

Node v25.9.0

### Transport

HTTP (Streamable HTTP)

### Description

`libofcongress_get_item`'s `format()` caps both `related_items` and `resource_links` at 5 entries in `content[]`. Originally this was a silent drop (see comments below); a first fix added an "… and N more" overflow note to both blocks. **Reopened:** disclosure isn't the same as access. An overflow count tells a `content[]`-onl

[Read the thread](https://github.com/cyanheads/libofcongress-mcp-server/issues/7) · 2026-05-24 · closed · 5 comments

### bug(search_subjects): returns non-LCSH authority records

### Server version

0.2.10

### mcp-ts-core version

^0.10.9

### Runtime

Bun

### Runtime version

Bun 1.3.11

### Transport

HTTP

### Description

`libofcongress_search_subjects` is described as returning Library of Congress Subject Headings for use as the `subject` filter in `libofcongress_search`, but the live endpoint response includes name-authority and children-subject records ahead of real subject headings. That can send callers to labels that are not LCSH subject headings and may not 

[Read the thread](https://github.com/cyanheads/libofcongress-mcp-server/issues/25) · 2026-06-27 · closed · 3 comments

### feat(get_item): expose research-critical metadata currently discarded

`libofcongress_get_item` describes itself as returning the full metadata record, but normalization drops several high-value fields already present in the requested `item` payload. The gap is most consequential for summaries, catalog identifiers, language/location context, and access restrictions.

## Proposal

Expand the existing output with a curated set of research-critical fields rather than forwarding raw LOC JSON: `summary`, `languages`, `locations`, `call_number`, `former_ids`, `original_f

[Read the thread](https://github.com/cyanheads/libofcongress-mcp-server/issues/36) · 2026-07-16 · closed · 2 comments

### feat(search): add collection_slug to complete the browse-to-search workflow

`libofcongress_browse_collections` returns stable collection slugs, but no MCP tool can use them to search inside that collection. The design documentation already describes the slug as a `libofcongress_search` input, while the actual search schema has no collection/part-of filter.

## Proposal

Add an optional `collection_slug` parameter to `libofcongress_search`. When present, route the existing query/filter/pagination shape through the corresponding collection endpoint so browse results becom

[Read the thread](https://github.com/cyanheads/libofcongress-mcp-server/issues/35) · 2026-07-16 · closed · 2 comments

### Most recent

### bug(errors): item_not_found and page_not_found reach the client with no recovery hint

### Server version

0.2.16

### mcp-ts-core version

0.10.14

### Runtime

Bun

### Runtime version

Bun 1.3.x

### Transport

HTTP

### Description

The `item_not_found` and `page_not_found` contract entries declare useful `recovery` metadata, but neither throw site passes `{ recovery: { hint } }`, so nothing reaches the wire. Both re-throw the service's message verbatim, and on a 404 that message is the generic `notFound('LOC resource not found')` raised inside `fetchJson` — it never names the

[Read the thread](https://github.com/cyanheads/libofcongress-mcp-server/issues/44) · 2026-08-10 · open · 0 comments

### feat(get_newspaper_page): request at=item,resource so newspaper_title, state, and edition stop coming back empty

### Use case

`libofcongress_get_newspaper_page` declares `newspaper_title`, `state`, and `edition` in its output schema, and never populates any of them. The request asks LOC for `?fo=json&at=resource`, and that projection returns exactly seven keys — `fulltext_file`, `iiif_manifest_url`, `image`, `pdf`, `segment_count`, `url`, `word_coordinates`. The `title`, `date_issued`, `part_of`, and `sequence` the handler reads are all `null` there, so `state` and `edition` are always absent and `part_of

[Read the thread](https://github.com/cyanheads/libofcongress-mcp-server/issues/42) · 2026-08-10 · open · 0 comments

### bug(search_subjects): count is the suggest endpoint's record tally, not the LOC item count it is described as

### Server version

0.2.16

### mcp-ts-core version

0.10.14

### Runtime

Bun

### Runtime version

Bun 1.3.x

### Transport

HTTP

### Description

`libofcongress_search_subjects` describes `count` as "Approximate number of LOC items carrying this heading." It is parsed from the third array of the id.loc.gov `/suggest/` OpenSearch response, which carries a per-suggestion description string — `"1 result"`, `"2 results"` — counting matching *authority records*, not catalogued items. `parseInt` r

[Read the thread](https://github.com/cyanheads/libofcongress-mcp-server/issues/41) · 2026-08-10 · open · 0 comments

### bug(pagination): LOC 404s out-of-range pages, so recovery guidance is skipped and a valid collection_slug is reported missing

### Server version

0.2.16

### mcp-ts-core version

0.10.14

### Runtime

Bun

### Runtime version

Bun 1.3.x

### Transport

HTTP

### Description

`fetchSearchJson` treats only HTTP 400 and 520 as "page out of range" (`allowStatus: [400, 520]` → `null` → the `pages: 0` sentinel handlers key their recovery notice on). LOC actually answers a past-the-end page with **404** on every endpoint except `/search/`:

| Endpoint | Out-of-range status | Result today |
|:---|:---|:---|
| `/search/` (no `f

[Read the thread](https://github.com/cyanheads/libofcongress-mcp-server/issues/40) · 2026-08-10 · open · 0 comments

### bug(get_item): object-form item.related_items violates the output schema and fails the call

### Server version

0.2.16

### mcp-ts-core version

0.10.14

### Runtime

Bun

### Runtime version

Bun 1.3.x

### Transport

HTTP

### Description

`libofcongress_get_item` fails outright for any item whose `item.related_items` entries are objects rather than strings. `RawLocItemResponse` types the field as `string[]` and `getItem` spreads it straight into the normalized `related_items: string[]`:

```ts
relatedItems.push(...(item.related_items ?? []));
```

LOC returns objects (`{ title, url 

[Read the thread](https://github.com/cyanheads/libofcongress-mcp-server/issues/39) · 2026-08-10 · open · 0 comments

### bug(tests): LOC_REQUEST_DELAY_MS override is a no-op, so the mocked suite sleeps ~137s

### Server version

0.2.12

### mcp-ts-core version

0.10.14

### Runtime

Bun

### Runtime version

Bun 1.3.14

### Transport

stdio

### Description

`bun run test` takes ~137s. The same suite with `LOC_REQUEST_DELAY_MS=0` in the environment takes ~975ms — a ~140x difference on a suite that mocks `fetch` and never reaches the network. The suite already tries to disable pacing per test, but the override never takes effect.

The cause is an ordering/caching interaction:

- `getServerConfig()` me

[Read the thread](https://github.com/cyanheads/libofcongress-mcp-server/issues/38) · 2026-07-16 · closed · 1 comment

### bug(browse_collections): returned slugs do not match LOC collection routes

### Server version

0.2.12

### mcp-ts-core version

0.10.14

### Runtime

Bun 1.3.14

### Transport

HTTP

### Description

`libofcongress_browse_collections` describes `slug` as the identifier within loc.gov collection URLs, but the extractor only matches URLs ending immediately after `/collections/<slug>/`. Current LOC results end in `/about-this-collection/`, so the regex misses and fabricates a title-derived fallback that often is not a valid route.

### Steps to reproduce

1. Call `libofco

[Read the thread](https://github.com/cyanheads/libofcongress-mcp-server/issues/37) · 2026-07-16 · closed · 1 comment

[See all 21 reports Pod holds for libofcongress-mcp-server](/mcp/libofcongress-mcp-server/issues) — of 40 qualified upstream.

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