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

Annotations already cover the safety profile (readOnly, non-destructive, open-world), so the bar is lower. The description adds genuinely useful behavioral context the annotations don't: newest-first ordering, 50-per-page cap, and $0.003 per-page billing. It stops short of describing edge cases like empty/private lists.

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?

Three tightly packed sentences: purpose first, then inputs, then return fields, then pagination/billing. Every clause carries information and none is redundant.

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 paginated list tool with no output schema, the description covers return fields, pagination limits, billing, and the input exclusivity rule. Combined with annotations that carry safety and world-openness, an agent has everything needed to call 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 baseline is 3, but the description adds the mutual-exclusion rule ('exactly one of username or url') that the schema itself does not express since all params are optional. That extra input-contract detail lifts it above baseline.

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 precise verb+resource ('Get the accounts a Bluesky user follows') and adds ordering ('newest first') and the accepted identifier forms. It is clearly distinguishable from the sibling bluesky_user_followers, which is the inverse relationship.

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 gives an input constraint ('provide exactly one of username or url') and the billing/page model, but never states when to use this versus alternatives such as bluesky_user_followers or bluesky_user_profile. Usage is implied by the verb rather than explicitly guided.

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