docs: add NEMAR tools documentation

* docs: add NEMAR tools documentation

Add NEMAR dataset discovery tools page documenting search_nemar_datasets
and get_nemar_dataset_details. Update tools index and mkdocs nav.

* docs: address review feedback for NEMAR tools

Match 3-column parameter table format from hed.md, expand NEMAR
abbreviation on first use in index.md, add missing return fields
(BIDS version, latest snapshot, how-to-acknowledge) to details docs.

* docs: expand BIDS and HED abbreviations on first use in NEMAR page

Author: neuromechanist

docs/osa/tools/index.md

@@ -28,6 +28,14 @@ Tools for working with the EEGLAB analysis toolbox.
 
 **Status:** Available
 
+### NEMAR Tools
+
+Tools for discovering and exploring BIDS-formatted datasets from the NeuroElectroMagnetic Archive (NEMAR).
+
+- [NEMAR Tools](nemar.md) - Dataset search and metadata retrieval
+
+**Status:** Available
+
 ---
 
 ## Common Tool Categories

docs/osa/tools/nemar.md

@@ -0,0 +1,94 @@
+# NEMAR Tools
+
+Tools for discovering and exploring EEG, MEG, and iEEG datasets formatted according to the Brain Imaging Data Structure (BIDS) from the NeuroElectroMagnetic Archive (NEMAR).
+
+NEMAR hosts hundreds of BIDS-formatted neuroscience datasets sourced from [OpenNeuro](https://openneuro.org/), covering various experimental paradigms and recording modalities. These tools query the NEMAR public API to help researchers find datasets matching their research interests.
+
+## Dataset Search
+
+### `search_nemar_datasets`
+
+Search NEMAR datasets with flexible text search and filtering. Fetches all datasets from the NEMAR API and filters client-side, returning compact summaries suitable for browsing.
+
+**Parameters:**
+
+| Parameter | Type | Description |
+|-----------|------|-------------|
+| `query` | string | Text search across dataset names, tasks, README, and authors (case-insensitive substring match) |
+| `modality_filter` | string | Filter by recording modality: `"EEG"`, `"MEG"`, `"iEEG"`, `"MRI"` (partial match, case-insensitive) |
+| `task_filter` | string | Filter by experimental task name, e.g. `"rest"`, `"gonogo"`, `"memory"` (partial match, case-insensitive) |
+| `has_hed` | boolean | If `true`, only return datasets with Hierarchical Event Descriptors (HED) annotations |
+| `min_participants` | int | Minimum number of participants required |
+| `limit` | int | Maximum results to return (default: 20, capped at 50) |
+
+**Example:**
+
+```python
+from src.assistants.nemar.tools import search_nemar_datasets
+
+# Find EEG datasets related to attention with at least 20 participants
+result = search_nemar_datasets.invoke({
+    "query": "attention",
+    "modality_filter": "EEG",
+    "min_participants": 20
+})
+
+# Find all datasets with HED annotations
+result = search_nemar_datasets.invoke({
+    "has_hed": True
+})
+```
+
+**Returns:** Formatted markdown string with matching dataset summaries, each showing dataset ID, name, modalities, tasks, participant count, and size. When no matches are found, returns a message listing the active filters and total dataset count.
+
+### `get_nemar_dataset_details`
+
+Get comprehensive metadata for a specific NEMAR dataset, including description, citation, licensing, experimental details, and README content.
+
+**Parameters:**
+
+| Parameter | Type | Description |
+|-----------|------|-------------|
+| `dataset_id` | string | Dataset identifier in the format `ds` followed by 4-6 digits (e.g. `"ds000248"`, `"ds005697"`) |
+
+**Example:**
+
+```python
+from src.assistants.nemar.tools import get_nemar_dataset_details
+
+result = get_nemar_dataset_details.invoke({
+    "dataset_id": "ds000248"
+})
+```
+
+**Returns:** Formatted markdown string with complete dataset information including:
+
+- OpenNeuro and NEMAR links
+- DOI and citation information
+- Authors, license, and BIDS version
+- Data characteristics (modalities, tasks, participants, sessions, file count, size, age range)
+- HED annotation status and version
+- Latest snapshot version
+- References, funding, acknowledgements, and how-to-acknowledge guidance
+- README content (truncated to 1500 characters for long entries)
+
+## Implementation Notes
+
+- The NEMAR API has no server-side search capability, so `search_nemar_datasets` fetches all datasets (~485) and filters client-side
+- Results are cached with a 5-minute TTL to avoid repeated API calls
+- The API endpoint is `https://nemar.org/api/dataexplorer/datapipeline`
+- Dataset IDs must match the pattern `ds` + 4-6 digits (validated before API calls)
+
+## External APIs
+
+| Service | Endpoint | Purpose |
+|---------|----------|---------|
+| NEMAR API | `https://nemar.org/api/dataexplorer/datapipeline/records` | Fetch all datasets for search |
+| NEMAR API | `https://nemar.org/api/dataexplorer/datapipeline/datasetid` | Fetch single dataset details |
+
+## Related Links
+
+- [NEMAR homepage](https://nemar.org)
+- [NEMAR Data Explorer](https://nemar.org/dataexplorer)
+- [OpenNeuro](https://openneuro.org/) (source platform for all NEMAR datasets)
+- [BIDS Specification](https://bids-specification.readthedocs.io/) (format standard for all NEMAR datasets)

mkdocs.yml

@@ -171,5 +171,6 @@ nav:
           - HED Tools: osa/tools/hed.md
           - BIDS Tools: osa/tools/bids.md
           - EEGLAB Tools: osa/tools/eeglab.md
+          - NEMAR Tools: osa/tools/nemar.md
       - Development: osa/development.md
       - Version Management: osa/version-management.md