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

Annotations cover the safety profile (readOnly, idempotent, openWorld), but the description goes well beyond: it scopes data to 'Public profile data only', discloses the paid x402/USDC-on-Base model at $0.001 per successful call, and — critically — tells the agent that an unpaid call returns a PaymentRequired object rather than an error. That is exactly the kind of non-obvious runtime behavior an agent needs.

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 purpose and returned fields are front-loaded, followed by the access constraint and the payment mechanics. Every sentence carries distinct information with no repetition of schema or annotations.

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 responsibly enumerates the return fields; with one simple parameter it explains the input; and it discloses access limits and payment flow. An agent has everything needed to call it correctly and interpret the response.

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 100% and the single 'actor' parameter is already documented as 'Handle (e.g. bsky.app) or DID'. The description adds no format or resolution detail beyond that, so the baseline 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+resource ('look up or verify a Bluesky account') and enumerates the exact payload (DID, handle, display name, bio, counts, creation time, avatar/banner, labels). This clearly separates it from siblings like bluesky_feed and bluesky_search, which return different resource types.

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?

'Use to look up or verify a Bluesky account' gives a clear triggering context, and the single-handle/DID input makes its niche obvious relative to feed and search tools. It stops short of naming which sibling to use for the alternative cases (e.g. searching posts), so no explicit exclusion.

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