List upstream MCP servers

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

Annotations already declare read-only and idempotent, so the safety profile is covered; the description adds value beyond them by disclosing the returned facets (health, circuit-breaker state, tool counts) and a relative cost signal. It does not discuss failure modes or whether unhealthy servers still appear, which keeps it below a 5.

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 sentences, both earning their place: the first front-loads what is returned, the second front-loads the cost-and-ordering advice. No filler, no restatement of the title.

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?

For a zero-argument, read-only discovery tool with no output schema, the description supplies the returned fields and the call-ordering guidance an agent needs. Nothing material is missing for correct invocation.

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 tool takes zero parameters, so there is no parameter meaning to convey and the schema is complete by construction; baseline 4 applies. The description correctly implies an unfiltered listing by adding no filtering or pagination talk.

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?

States a specific verb and resource ('List the upstream MCP servers') plus scope ('multiplexed by this gateway') and the payload contents (health, circuit-breaker state, tool counts). This clearly separates it from list_tools/search_tools (tools, not servers) and gateway_status, without needing to name a sibling.

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?

'Cheap: call this first to orient yourself' gives concrete when-to-use guidance and sequencing relative to the rest of the gateway toolset. It stops short of naming an explicit alternative or a when-not condition, so it is clear context rather than full routing logic.

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