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

With readOnlyHint=true already in the annotations, the description adds meaningful behavioral context: it returns full bodies, supports cursor-based pagination for the next page, and explicitly disclaims selector discovery. This goes beyond what the schema and annotations alone convey.

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 two tight sentences with no filler: main purpose, pagination alternative, and exclusion are all packed in efficiently. The core behavior is front-loaded in the first sentence.

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 read-only tool with two optional parameters and no output schema, the description covers the return type, paging behavior, and the prerequisite that selectors be pre-chosen. The main gaps are whether cursor and selectors can be combined and where the cursor originates, but these are minor for this simple 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?

Schema description coverage is 0%, so the description must compensate for the bare parameter names. It does: 'selectors' are described as previously chosen selector values, and 'cursor' is tied to fetching the next page. It still leaves details like mutual exclusivity and formatting unspecified.

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 states a specific verb and resource: it returns 'full bodies' for already-chosen selectors or the next page of a cursor. The closing exclusion, 'Does not discover selectors,' clearly separates it from discovery-oriented siblings like web3_search and web3_lookup.

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 phrase 'selectors you already chose' establishes that the tool is used after selector selection, and 'Does not discover selectors' states when it should not be used. It does not explicitly name which sibling should be used for discovery, so the routing is implied rather than fully explicit.

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