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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's added value is the note that each limit carries 'the date they were checked' — a genuinely useful staleness signal for a static reference tool. It stops short of saying whether limits are per-platform objects, how large the payload is, or whether any platform is unsupported, but for a read-only lookup that is a minor omission.

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?

A single front-loaded sentence that starts with the action and lets the field list do the work; there is no filler or repetition. The dense run-on list of limits is slightly hard to scan but every clause maps to real returned content.

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 no output schema, one optional enum parameter, and rich read-only annotations, the description does the necessary work by enumerating return content and flagging the checked date. It is close to complete; only the shape of the returned data and the default behavior when platform is omitted remain under-specified.

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 0%, so the description must carry the only parameter, and it does add partial meaning: the enum members are restated inline and '(or one of them)' conveys that the parameter is optional and that omitting it returns all platforms. The phrasing is ambiguous rather than explicit, and it does not state the default behavior plainly or say what an invalid platform does.

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 opens with a specific verb and resource ('Returns the limits for posting to Instagram, Facebook, YouTube, TikTok, LinkedIn and X') and enumerates exactly which limits come back (text length and counting rules, hashtags, video length, file size, codecs, frame rate, Stories, posting cadence). That enumeration implicitly distinguishes it from validator siblings like check_caption and check_video, but it never explicitly contrasts with them or with get_image_sizes, which also touches size/shape.

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 is only implied: the parenthetical '(or one of them)' suggests calling with no platform returns all six and supplying one narrows the result. There is no explicit when-to-use statement, no guidance on pairing it with check_caption/check_video/get_image_sizes (the same limits are presumably the rules those tools enforce), and no when-not-to-use case.

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