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

No annotations are provided, so the description carries the full burden. It discloses the payload shape (per-chain availability plus block height), which signals a read-only aggregate, but says nothing about freshness/latency, rate limits, or whether availability is cached — gaps that matter for a 'live' status 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?

Front-loaded with the resource and scope, then usage, then the exclusion. Three tight sentences with zero filler, and the most decision-relevant information (what it lists and when not to use it) appears first.

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 must convey the return shape, and it does so concisely (chains, availability, block height). It stops short of describing ordering, field naming, or how many chains appear if some are offline, which is a minor but real gap for a discovery tool.

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?

The tool takes zero parameters, so there is nothing to document and the schema is trivially complete. Per the rubric baseline for a 0-param tool, 4 is appropriate; no parameter knowledge is missing.

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?

States a specific verb and resource ('Every chain this service supports') and enumerates the exact scope (BTC/ETH/XMR/ZEC) with the returned attributes (live availability, block height). It explicitly distinguishes itself from the sibling chain_status, so an agent can route without inspecting either 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?

Provides explicit when-to-use triggers (user asks which chains are supported, which nodes are online, chain heights) and an explicit when-not with the named alternative ('for detail on one chain, use chain_status'). No inference required.

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