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

Annotations already cover readOnly, idempotent, and openWorld, and the description's 'Read-only' sentence merely restates that. However, it adds genuinely new behavioral context: the exact fields per account, cursor-based paging, and a billing model of 1 credit per result with a 1-credit minimum per request, which is not derivable from annotations or schema.

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?

Four short sentences, front-loaded with purpose then return shape, paging, and cost. The 'Read-only: returns public data and changes nothing' sentence is largely redundant with readOnlyHint and destructiveHint=false, the only real waste.

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 usefully enumerates the returned fields and explains pagination and credit cost, which is enough for a two-parameter list tool. Minor gaps remain around end-of-list behavior and error/empty-result handling, but nothing blocking an agent from calling it correctly.

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 coverage is 100%, so both parameters are already fully documented, including the cursor/nextCursor contract and the get-user lookup hint. The description adds only the reiteration that userId is numeric and that cursor pages the list, so the baseline of 3 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 and resource ('List the accounts an X user follows') and pins the required identifier type ('numeric user ID'), which unambiguously conveys direction (following, not followers). It does not explicitly name its nearest sibling x_get_followers, so the differentiation is implied rather than spelled out.

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?

Gives procedural guidance for use ('using its numeric user ID', 'omit cursor for the first page') but no when-to-use versus when-not guidance, and never mentions x_get_followers or x_get_user as the alternative paths. An agent must infer the choice from the tool name alone.

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