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

Annotations supply readOnlyHint and openWorldHint, and the description adds genuinely non-redundant behaviour: the data is live, and each call costs $0.002 USDC via x402, which is critical for an agent deciding whether to invoke it. It does not cover things like rate limits or cache staleness, so it falls short of 5.

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?

Three short sentences, front-loaded with what the tool returns, then the usage trigger, then the cost. No filler; every sentence carries information the agent needs.

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?

With no output schema, the description carries the return-value burden and does so by listing the delivered metrics. Payment requirement, live-ness and the healthy flag are all disclosed, so an agent has everything needed to call and interpret it.

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 100%, so the single 'chains' parameter is already documented as comma-separated with a default of all five. The description enumerates the five chain names, which slightly reinforces the default set, but adds no new syntax or filtering semantics. Baseline 3 applies.

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?

Names the exact resource (live health of five named chains) and enumerates the specific fields returned: latest block, seconds since it, average block time, gas price, base fee, utilisation and a healthy flag. This is plainly distinguishable from siblings like 'gas', 'rpc' or 'btc_fees' without opening any schema.

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?

"Check before sending transactions" gives an explicit, actionable when-to-use. It stops short of naming an alternative or a when-not-to-use condition, so it is clear context rather than full routing guidance.

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