ru-marketplace-mcp

Which Marketplaces Are Loaded

marketplace_sources

Read-onlyIdempotent

Check which marketplace connectors are actually mounted before querying. Distinguishes an unavailable source from one that returned no results.

Instructions

List which connectors this unified server actually mounted.

Why this exists

Connectors are imported defensively, so a missing dependency removes a marketplace instead of killing the server. That is the right failure mode, but it is invisible from the client: absent tools look the same as a source that simply found nothing. Call this before concluding a marketplace has no results — if it is in skipped, it was never queried at all.

Return Format

MarketplaceSourcesResponse: {mounted, skipped, mounted_count, skipped_count, capabilities, server_version}. skipped maps source name to the reason it is unavailable: an import error (usually a missing optional dependency) or an explicit MARKETPLACE_SOURCES deselection.

Error Format

Never raises ToolError: pure introspection of the mounted connectors — a failed import is recorded in skipped instead of being raised.

Input Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Output Schema

TableJSON Schema

Name	Required	Description	Default
`mounted`	No
`skipped`	No
`capabilities`	No
`mounted_count`	No
`skipped_count`	No
`server_version`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv2.1.0Sep 9, 2026
- addedOutput schema / properties / capabilities
```
Added value: +{}
```
First observedv1.5.1Aug 17, 2026

TDQS

A4.6/5.0

Behavior4/5

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

Annotations already carry the read-only/idempotent/no-destructive profile, but the description adds genuinely non-obvious behavior: the defensive import model, the existence of the 'skipped' set, and the explicit guarantee that it never raises ToolError. It stops short of the annotation-free ideal but goes well beyond the safety hints.

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?

Front-loaded with the one-line purpose, then organized under 'Return Format' and 'Error Format' headings. Slightly verbose in the 'Why this exists' rationale, but every sentence carries information an agent needs.

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?

Despite an output schema existing, the description still summarizes the response shape and, more importantly, explains the semantics of 'skipped' (import error vs. explicit deselection). It also covers the error contract, so an agent has everything needed to interpret results correctly.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline is 4. The description correctly implies a parameterless introspection call without inventing or misrepresenting inputs.

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 and resource ('list which connectors this unified server actually mounted') and is unmistakably distinct from every sibling search/card tool. An agent can tell it apart without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicit when-to-use: 'Call this before concluding a marketplace has no results.' It also names the failure mode that makes that necessary (absent tools look the same as an empty source), which is exactly the routing guidance an agent needs.

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