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

Goes well beyond the annotations: it discloses the 404 conditions (nonexistent or protected account), explains what protected means for visibility, and gives a full billing model including the one-time profile lookup on the first page only. The pagination contract and credit formula are exactly the kind of operational detail annotations cannot carry.

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 purpose, then error conditions, then cost, then pagination — a sensible ordering with no filler. Minor redundancy: 'Billed per post returned' is immediately restated by the fuller credit formula.

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?

For a 3-parameter read tool with no output schema, the description covers everything an agent needs: what is returned, where media URLs live, failure modes, cost, and how to page. Nothing material is left to inference.

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 the baseline is 3, but the description adds real meaning about the user/cursor relationship: the first page resolves {user} and bills a lookup, while later pages carry the account in the cursor. That explains why both parameters coexist in a way the schema alone does not.

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 (get an account's posts with media) and immediately narrows the scope to the Media tab: own posts carrying photos, videos, or GIFs, newest first. That distinguishes it cleanly from siblings like get_x_user_posts and get_x_user_replies without needing to open either 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?

Usage context is clear from the Media-tab framing and the explicit pagination instruction ('when meta.nextCursor is set, call again with cursor set to it'). It does not, however, name an alternative sibling for the unfiltered case (e.g., get_x_user_posts for all posts), so the when-not guidance is left implicit.

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