check_api_status

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

No annotations are provided, so the description carries the full burden. It discloses that the tool reports active source, failover state, and latency—which are read-only diagnostic behaviors. There's no mention of side effects, but given the read-only nature described, this is reasonably transparent for a status-check 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?

Single sentence, front-loaded with the core purpose, and efficiently lists what it reports (active source, failover, latency). Zero waste.

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 has no inputs, no output schema, and no annotations, making it a simple diagnostic call. The description explains the tool's output scope well (active source, failover, per-source latency). Could specify whether this is an administrative/ops tool or if it has rate limits, but this is a minor gap for a zero-parameter status checker.

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 has zero parameters and 100% schema coverage (empty object), so there's nothing to describe. The baseline for 0 params is 4; the description fully explains what the tool returns without needing parameter details.

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 checks real-time availability/latency of VIES and BZSt upstream sources, using specific verbs ('check', 'shows'). It distinguishes from the sibling tool validate_vat_id, though it doesn't explicitly name the alternative.

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 description implies this is a monitoring/diagnostics tool used to check source availability, which contrasts with validate_vat_id's purpose. However, it doesn't explicitly state when to use this vs the alternative or when NOT to use it.

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