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

Annotations already declare readOnly/openWorld, but the description adds substantial context beyond them: $0.01 per successful call, invalid input and not-found results are free, and payment is passed via _meta["x402/payment"] over USDC on Base. That is exactly the kind of cost and prerequisite disclosure an agent needs before invoking a paid tool.

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?

One dense paragraph, front-loaded with the lookup scope and returned fields, then the commercial terms. Every clause carries information, though the pricing sentence is packed tightly and could be split for readability without loss.

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 the 'shared social schema' convention, and it covers input forms and billing. It stops short of noting rate limits, caching, or what a 'no match' response looks like, which would matter for error handling.

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 parameter's description already spells out handle vs. did:plc/did:web vs. bsky.app URL. The description restates those accepted forms in prose without adding new syntax or defaults, so the schema does the heavy lifting — baseline 3.

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 ('Profile Lookup' of 'one public Bluesky account') and enumerates the returned fields (display name, bio, counts, verification, avatar, creation time, DID). The word 'one' plus the input forms (handle, DID, URL) clearly separates it from list/search siblings like bluesky_search and bluesky_posts.

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?

Implied usage is clear — fetch a single known account — and the pricing/charging rules help an agent decide whether to call. However, no sibling is named and there is no explicit when-not guidance (e.g., use bluesky_search when you only have a display name, or x_profile for the other network); the agent must infer routing.

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