Routing fallback — siblings to a flagged endpoint

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

Despite no annotations, the description discloses key behaviors: filters out 7-day-dead and 1-hour-erroring candidates, ranks by uptime+latency, costs $0.005 USDC, and falls back to taskClass if url is unknown. It lacks details on edge cases like missing both parameters.

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-sentence paragraph efficiently conveys purpose, input, behavior, and usage hint. Every sentence is informative with no redundancy, and the core action is front-loaded.

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 main use case, filtering criteria, cost, and parameter guidance. Missing return format details and error handling (e.g., no alternatives found), but is sufficient given no output schema and low complexity.

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?

Schema has 100% coverage, but the description adds context beyond field descriptions: explains how url and taskClass are used as match keys, the ranking logic, and implies default limit of 5. This enriches the agent's 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 clearly states the tool's action: 'returns up to 5 healthy sibling endpoints' when given a flagged URL or taskClass hint. It distinguishes itself from sibling tools like preflight by specifying it is used after preflight returns ok=false, providing a clear purpose.

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 instructs when to use: 'Use this immediately after preflight returns ok=false'. It also explains the different parameter combinations (url, taskClass, or both) and when to choose each, providing strong guidance.

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