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

Annotations already declare readOnly/openWorld/non-destructive, so the safety profile is covered. The description adds genuinely useful behavioral context beyond annotations: newest-first ordering, 50-per-page pagination, and per-page billing ($0.003), which an agent needs for cost/scope decisions.

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 tight sentences with zero waste; the core purpose and identifier constraint are front-loaded, followed by return fields, pagination, and cost. Every sentence earns its place.

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 return fields (handle, display name, DID, bio, verification, picture, join date) and covers pagination and billing. Minor omissions like rate limits or auth needs remain, but the definition is complete enough to call 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 the schema documents the parameters well (baseline 3). The description adds value by stating the 'exactly one of username or url' exclusivity constraint, which the schema does not enforce (0 required params), directly guiding correct invocation.

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 ('Get a Bluesky user's followers'), plus the ordering ('newest first') and the accepted identifier forms (handle, DID, profile URL). This clearly distinguishes it from the sibling bluesky_user_following.

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 clear context on how to invoke it and an explicit input constraint ('provide exactly one of username or url'). It does not, however, name the alternative sibling (bluesky_user_following) or state when not to use this tool.

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