source_status

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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, so the safety profile is covered. The description adds a valuable behavioral guarantee: 'Always returns an evaluable status rather than an empty result set' – this goes beyond annotations by explaining the tool's output semantics and its purpose in distinguishing 'no data' from 'source down'. This extra context improves agent understanding of the return behavior.

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?

The description is two sentences long plus a use_case tag, with no filler. The primary action is front-loaded ('Report reachability and latency'), and the use_case adds practical context. Every sentence earns its place, making it highly efficient.

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-parameter, read-only health check tool, the description covers the essential aspects: what it reports, when to use it, and its non-empty return guarantee. The output schema exists, so return details are already structured. Nothing critical is missing for an agent to invoke this tool correctly.

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?

There are zero parameters, so the description has no parameter details to add. Per the rubric, a tool with 0 params gets a baseline of 4. The schema has no properties, so there is nothing to clarify; the description correctly focuses on behavior and use case.

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 specific verb and resource: 'Report reachability and latency of both upstream sources.' This clearly distinguishes it from sibling data-query tools like list_cantons or get_public_holidays, which fetch domain data rather than report on system health. The use_case tag reinforces this by framing it as a pre-query health check.

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?

The use_case tag explicitly states when to use this tool: 'Health check before a batch of queries, or to distinguish no data from source down.' This gives clear context for selection, though it does not name any alternative tools directly. The distinction is implicit: this tool is for checking source availability, not for querying holiday data, so the usage guidance is solid but not exhaustive.

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