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

No annotations exist, so the description carries the full burden. It usefully discloses that media is fetched server-side with a 25 MB per-item cap and that scheduling has a 10-minute minimum lead time, but says nothing about failure behavior, per-platform validation, permission requirements, or what a successful call returns.

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 dense sentences with zero filler. The draft/scheduled distinction leads, and the hard constraints follow as supporting detail.

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 5-parameter mutation tool with no annotations and no output schema, the description covers the two non-obvious parameters well but leaves gaps: the tool's return value is unexplained, and there is no mention of cross-platform constraints despite a required multi-platform array.

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 already 80%, and the description still adds real semantics on top: it states the 10-minute future constraint on scheduled_at (schema only says 'ISO 8601. Omit for a draft') and the server-side fetch plus 25 MB limit on media_urls (schema only says public https URLs). Caption and workspace get no extra meaning, which keeps it below 5.

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 ('Create a ... post') and immediately splits the two modes the tool supports: draft vs scheduled. It is clearly distinguished from update_post/cancel_post by the creation framing, though it never names a sibling explicitly.

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 clear selection logic: supply scheduled_at for a scheduled post, omit it for a draft, and the schedule must be ≥10 minutes ahead. No exclusions about when to prefer update_post or how to publish immediately, but the primary branch an agent must decide is spelled out.

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