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

Annotations already declare readOnlyHint=true and idempotentHint=true, and the description adds complementary context: 'Read-only. No key needed.' It also discloses the exact return shape for both modes, which is valuable beyond the annotations. No contradiction exists.

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 dense but tightly organized: purpose, mode breakdown, when-to-use, exclusions, return shapes, and auth note. Every sentence adds useful information and the key differentiator 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?

Given no output schema and low schema coverage, the description does a strong job covering inputs, outputs, exclusions, and authentication. Minor gaps remain around the precise semantics of family/prefer/candidates, but the overall context is sufficient for an agent to select and call the 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?

Schema description coverage is only 14%, so the description must compensate. It explains what='chain' vs what='route' and maps optional parameters to each mode (family, candidates, prefer for chain; chain, method, need for route). However, the meaning of 'family', 'prefer', and 'candidates' is left vague, and the schema itself provides no further help.

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 establishes what the tool does: it returns a recommendation from live measurements, with two explicitly distinguished modes ('chain' and 'route'). It names the resource and the ranked output, and it differentiates itself from siblings by saying what it is not for (price, gas, making calls).

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 gives explicit when-to-use guidance: 'Use it when you can choose the chain or the lane and want the measured answer.' It also provides direct exclusions and alternatives: not for price (get_quote), not for gas (get_prices), not for making the call (rpc_call).

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