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

Annotations already declare readOnly, idempotent, and closed-world, so safety is covered. The description adds genuinely new behavioral context: the tool is BTC-only by default and the exit_desk_full subscription expands coverage to ETH plus venue failure data, which materially affects expectations.

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 dense sentences, front-loaded with the resource and metric list, then the tier note. Every clause carries information; 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?

With no output schema, the description compensates by naming the returned metrics and the tier-dependent scope expansion, which is about as complete as an agent needs for a no-argument snapshot tool. It does not mention refresh cadence or units, a minor gap.

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?

Zero parameters, so there is nothing for the description to disambiguate; the 100% schema coverage baseline plus no-param rule places this at 4. The description appropriately spends no words on arguments.

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 a specific resource (BTC two-sided depth) and enumerates the outputs (HHI, effective/top venue, venue depth), which lets an agent distinguish it from generic depth tools like depth_episodes and liquidity_tiers. It lacks an explicit verb, but for a zero-param read tool the metric list is the substance.

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?

Implies usage context (BTC depth concentration today) and flags a subscription tier gate, but never states when to prefer this over siblings such as depth_episodes or liquidity_tiers. No when-not guidance.

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