list_sources

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

States 'Behavior: read-only, no side effects' and that it never throws for unreachable backends (reports down). Describes return fields. Could mention rate limits or auth, but it's a simple listing tool.

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?

Three sentences: purpose, when to use, behavior, and a note on error handling. Front-loaded with key info, no fluff.

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?

Covers what the tool does, when to use, behavior, error handling, return format (name, type, URL, signal types, status), and relationship to sibling tool list_services. No output schema needed; description provides sufficient detail.

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?

No parameters exist (input schema is empty with 100% coverage). The description adds meaning about the tool's purpose but doesn't need to explain parameters since there are none.

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 clearly states the tool lists configured observability backends and their reachability, specifies backend types (Prometheus, Loki, connector), and differentiates from sibling tool list_services by noting that list_services shows what is monitored within these sources.

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?

Explicitly provides when-to-use guidance: 'call this first to learn which source names exist and are healthy before passing source to other tools, or to debug why a query returns no data.' Also mentions related tool list_services.

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