# json_objlen

Get the number of keys in the object at path. Args: key: The name of the key path: The path in the JSON document Returns: Number of keys or error message

Agent View of the PolicyLayer registry record for `json_objlen`. HTML page: https://policylayer.com/tools/aws/json-objlen

## Facts

- Tool: `json_objlen`
- Server: AWS (`@awslabs/mcp`) — https://policylayer.com/tools/aws.md
- Install: `npx -y @awslabs/mcp`
- Homepage: https://github.com/awslabs/mcp
- Risk category: Read (Low risk)
- Registry record: grade F, identity verified
- Server rate-limited: no
- Parameters: 0
- Recommended policy verdict: Allowed

## Example call (MCP tools/call, JSON-RPC 2.0)

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "json_objlen",
    "arguments": {}
  }
}
```

## Why json_objlen is rated Low

The tool performs a simple introspection of JSON data structure (counting keys), which is a read operation with no side effects. No data is modified, deleted, or executed. The blast radius of misuse is minimal—an agent could only learn the structure of JSON objects it has access to read.

From the tool's own definition: "Tool description states 'Get the number of keys in the object at path' with return value 'Number of keys or error message'. This is a read-only query operation that retrieves metadata about a JSON structure without modifying, executing, or deleting anything."

## Use case

AI agents call json_objlen to retrieve information from AWS without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

## Recommended policy (PolicyLayer)

Verdict: **Allowed**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches AWS:

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "json_objlen": {}
  }
}
```

## Other tools on AWS (299)

- `bulk_delete_by_criteria` — Destructive — https://policylayer.com/tools/aws/bulk-delete-by-criteria.md
- `cache_delete` — Destructive — https://policylayer.com/tools/aws/cache-delete.md
- `cache_delete_many` — Destructive — https://policylayer.com/tools/aws/cache-delete-many.md
- `cache_delete_multi` — Destructive — https://policylayer.com/tools/aws/cache-delete-multi.md
- `cache_flush_all` — Destructive — https://policylayer.com/tools/aws/cache-flush-all.md
- `delete` — Destructive — https://policylayer.com/tools/aws/delete.md
- `delete_access_key` — Destructive — https://policylayer.com/tools/aws/delete-access-key.md
- `delete_datastore` — Destructive — https://policylayer.com/tools/aws/delete-datastore.md
- `delete_group` — Destructive — https://policylayer.com/tools/aws/delete-group.md
- `delete_image_set` — Destructive — https://policylayer.com/tools/aws/delete-image-set.md
- `delete_instance_in_series` — Destructive — https://policylayer.com/tools/aws/delete-instance-in-series.md
- `delete_instance_in_study` — Destructive — https://policylayer.com/tools/aws/delete-instance-in-study.md
- `delete_patient_studies` — Destructive — https://policylayer.com/tools/aws/delete-patient-studies.md
- `delete_resource` — Destructive — https://policylayer.com/tools/aws/delete-resource.md
- `delete_role_policy` — Destructive — https://policylayer.com/tools/aws/delete-role-policy.md
- `delete_series_by_uid` — Destructive — https://policylayer.com/tools/aws/delete-series-by-uid.md
- `delete_study` — Destructive — https://policylayer.com/tools/aws/delete-study.md
- `delete_user` — Destructive — https://policylayer.com/tools/aws/delete-user.md
- `delete_user_policy` — Destructive — https://policylayer.com/tools/aws/delete-user-policy.md
- `detach_user_policy` — Destructive — https://policylayer.com/tools/aws/detach-user-policy.md
- `json_arrtrim` — Destructive — https://policylayer.com/tools/aws/json-arrtrim.md
- `json_clear` — Destructive — https://policylayer.com/tools/aws/json-clear.md
- `json_del` — Destructive — https://policylayer.com/tools/aws/json-del.md
- `list_pop_left` — Destructive — https://policylayer.com/tools/aws/list-pop-left.md
- `list_trim` — Destructive — https://policylayer.com/tools/aws/list-trim.md
- `remove_instance_from_image_set` — Destructive — https://policylayer.com/tools/aws/remove-instance-from-image-set.md
- `remove_series_from_image_set` — Destructive — https://policylayer.com/tools/aws/remove-series-from-image-set.md
- `set_pop` — Destructive — https://policylayer.com/tools/aws/set-pop.md
- `sorted_set_remove_by_lex` — Destructive — https://policylayer.com/tools/aws/sorted-set-remove-by-lex.md
- `sorted_set_remove_by_score` — Destructive — https://policylayer.com/tools/aws/sorted-set-remove-by-score.md
- …and 269 more: https://policylayer.com/tools/aws.md

## For agents

This record is a snapshot. Live verdicts and the full registry:

- Check every server in your MCP config at once: `npx -y policylayer stack`
- Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md)
- Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events`

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Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=aws · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/aws