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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so safety is covered. The description adds real value beyond that: the return shape, that it covers every chain in the directory, the spotlight-first ordering (Base, Ethereum, Solana…), and the 'real agent tooling vs announcement' distinction. It stops short of pagination or truncation behavior, keeping it from a 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?

Front-loaded into USE WHEN / NOT FOR / RETURNS blocks with no filler; each sentence routes the agent or describes the payload. The trailing 'Example: {}' is a harmless confirmation that no arguments are required.

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?

Although there is no output schema, the description supplies the exact return shape ({ total, chains: [{ name, count }] }), ordering, and directory coverage, so nothing an agent needs to call or interpret 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?

Only one parameter (response_format) with 100% schema description coverage, so the schema already documents it fully. The description notes the payload is JSON but never explains response_format or its markdown/json enum, so it adds no meaning beyond the schema — the baseline 3 for high coverage 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?

States a specific verb+resource (list chains) with scope: every blockchain in the directory with resource counts. It explicitly names the siblings it is not (onchain_agent_list_categories, onchain_agent_get_agent_economy), so an agent can route without opening other schemas.

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?

Leads with an explicit 'USE WHEN' condition (need valid chain names before filtering onchain_agent_search_resources) and a second motivating case. 'NOT FOR' clauses name both alternatives and the exact sibling to use instead for each.

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