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

Annotations already declare this a safe, idempotent read, and the description adds information the annotations cannot carry: per-row billing, the fact that limit caps both rows and cost, and that results are untrusted user-generated content. That is real behavioral value beyond the structured fields.

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: purpose, routing, return shape, and cost/trust caveats, in that order of importance. Every sentence earns its place and the core action is front-loaded.

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?

No output schema exists, but the description enumerates the returned columns (pk, code, taken_at, media_type, like_count, comment_count), and it covers cost and trust caveats. An agent has everything needed to call it 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 both parameters are already documented, which sets a baseline of 3. The description goes further by tying limit to cost ('limit caps both rows and cost') and restating the sort default with allowed values, adding meaning the schema does not express.

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 (rank), resource (Instagram posts), scope (whole database), and the sort key with its default. It also explicitly names the two siblings it is not (get_user_medias, search_media_captions), so an agent can route without opening any schema.

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 an explicit when-to-use ('find the most engaging content overall') plus the exact conditions that select the alternatives: one account vs. topic filtering. Nothing is left to inference.

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