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

With no annotations provided, the description carries the full burden of behavioral disclosure. It discloses that this is a lookup/read operation and lists the returned fields, but it does not mention network defaulting behavior, error handling for unknown IDs, or any other side effects. This is acceptable but not rich.

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 a single front-loaded sentence that wastes no words. It states the action, the key input, and the expected output in a clear and efficient structure.

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?

For a simple two-parameter lookup with no output schema, the description covers the essential inputs and outputs. It could be more complete by noting the network parameter's role and handling of missing blockchains, but the core behavior is sufficiently specified.

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 50%: chainId is documented as 'The blockchain ID' and network has an enum plus default but no description. The tool description adds that the lookup is 'by its ID' and clarifies what is returned, but it does not add significant meaning to the network parameter beyond what the schema already expresses.

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 opens with a specific verb and resource: 'Look up a blockchain by its ID'. It also names the returned information (name, VM type, Subnet/L1), making the tool's scope clear and distinguishing it from sibling lookup tools like blockchain_lookup_subnet or blockchain_lookup_address.

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 implies usage when you already have a blockchain ID and want its metadata, but it does not explicitly explain when to choose this tool over similar lookup tools in the sibling list, nor does it mention exclusions or alternative tools.

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