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

With no annotations provided, the description carries the behavioral disclosure burden. It does disclose a cost behavior ('Billed $0.003 per page'), which is useful for an agent making economical calls, and the schema already documents pagination and page size. However, it omits other behavioral context like rate limits, auth requirements, or response shape. The cost signal is real but limited.

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?

Two sentences with zero waste; the core action is front-loaded and the billing caveat follows naturally. This is a model of concise, scannable tool description—every word 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?

The schema covers all parameter meanings, and the tool is a straightforward keyword search. However, with no output schema or annotation, the description does not tell the agent what fields/results to expect, nor does it mention any preconditions beyond the billing note. For a simple search tool this is minimally viable, but it leaves the return payload undocumented.

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%, so the schema fully documents the six parameters and their formats. The description adds no parameter-specific semantics beyond the schema, such as query syntax or date formats, but it is not required to do so because the schema is complete. This aligns with the baseline of 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?

The description states a specific verb, resource, and scope: 'Search Bluesky posts by keyword.' The resource 'posts' distinguishes it from the sibling search_bluesky_users, though it does not explicitly name the alternative. It is clear but lacks an explicit sibling differentiation, so it does not earn a 5.

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 provides no guidance on when to choose this tool over the many alternative search tools (e.g., search_bluesky_users, search_twitter). It does not state exclusions, prerequisites, or context that would help an agent decide between this and a sibling. The only extra signal is billing, which is cost-related rather than usage-direction.

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