List Available Marketplaces

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

Annotations already establish read-only, idempotent, non-destructive behavior, so the bar is lower. The description adds useful behavior beyond annotations: it reports installation-level availability and distinguishes connector installation issues from marketplace refusals.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tight sentences. The first states the core purpose directly; the second provides actionable guidance with no filler or redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The tool is low-complexity: no parameters, output schema present, and safety annotations cover side effects. The description explains what it reports, when to call it, and what distinction it makes. The only minor gap is not explicitly contrasting it with the similarly named sibling 'marketplace_sources.'

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has zero properties, so there is no parameter semantics for the description to elaborate. Per the baseline for parameterless tools, this is a 4.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a concrete action ('Report') and a specific resource ('which marketplaces this installation can actually query'). It also distinguishes the tool's diagnostic role from the comparison tools by noting it separates a missing connector from a marketplace refusal.

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

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

It explicitly tells the agent when to call this tool: 'Call this first when a comparison comes back partial.' It also explains why that matters by naming the two distinct failure causes and noting they need 'completely different fixes.'

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