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

Annotations already declare readOnlyHint=true and destructiveHint=false, covering the safety profile. The description adds context on what the tool returns (per-rail status, latency, last incident, composite health score) and the geographic scope of supported rails. No contradictions with annotations.

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 three sentences, front-loaded with the core purpose, and provides the key rail list and usage guidance without unnecessary filler. Every sentence earns its place.

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 simple read-only status tool with two optional parameters and an output schema, the description fully covers what an agent needs: purpose, return fields, supported rails, and a usage trigger. Given the output schema exists, no need to detail return format.

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 already documents both parameters with descriptions, and coverage is 100%, so a baseline of 3 applies. The description adds semantic mapping of rail codes to regions (PIX=Brazil, SEPA=Europe, FedACH=US, etc.), which goes beyond the schema's bare names. This enriches parameter understanding.

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 uses a specific verb ('Get') with a clear resource ('live health status of local payment rails') and states the return fields. It differentiates from sibling oracle tools by focusing on payment rails relevant to settlement, listing key rails. This is a strong purpose statement.

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 explicitly tells the agent when to call this tool: 'before domestic or regionally-specific settlements to confirm the destination rail is healthy.' While it provides clear usage context, it does not mention when not to use it or name alternative tools, so it stops short of a full 5.

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