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

With no annotations, the description carries the transparency burden. It discloses the read-only nature via 'List,' the dynamic filtering behavior via 'currently qualify,' and the evaluation basis through 'success/latency history,' plus a 'FREE' cost signal. It does not explain pagination or return formatting, but those are minor for a parameterless 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?

The entire description is one short sentence plus a cost label. It front-loads the important cost signal, states the exact resource and selection criterion, and contains no filler.

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 parameterless list operation, the description sufficiently tells the agent what is returned and why. It could be slightly more complete by contrasting with list_discovered_apis or describing the returned fields, but nothing essential to invoking this tool is missing.

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 schema already fully covers invocation and the 100% schema description coverage confirms nothing is undocumented. The baseline of 4 applies because no parameter documentation is needed.

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 names a specific action and object: 'List upstream APIs that currently qualify for the Verified routing tier.' It also adds the selection basis ('success/latency history'), which clearly differentiates it from sibling list_discovered_apis.

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 phrase 'currently qualify for the Verified routing tier' makes it clear this tool is for retrieving verified-tier APIs, and the zero-parameter schema means there is no ambiguity about invocation. It does not explicitly mention alternatives or when-not-to-use conditions, so it stops short of a 5.

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