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

Annotations only declare readOnly/openWorld; the description adds real behavior: no per-account handle resolution, so it's cheap, exact totals for typical collections, exact:false + cursor for very large ones, and relay-served by default. These are non-obvious traits 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?

Front-loaded with the purpose and example, then paging behavior, then relay notes. Efficient overall, though some comma-spliced clauses ('cursor,call again') are dense and slightly hard to parse.

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 an output schema present, return values need not be explained, and the description still covers the exact:false shape, paging, and relay default. Complete enough for correct invocation.

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 meaning beyond the schema: relay defaults to the public Bluesky relay and cursor counts must be summed rather than overwritten. Useful additive context.

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: counting accounts that publish a given collection across the network, with a concrete example query. Clearly distinguishes it from siblings like count_records and list_repos_by_collection.

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?

Explains the paging protocol (exact:false + cursor, call again and ADD counts, referencing count_records) and the relay override condition. Gives clear context but does not state exclusions vs. list_repos_by_collection beyond the 'count' framing.

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