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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), so the description correctly spends its space elsewhere: it discloses that limits do not inspect a file, do not guarantee publishing eligibility, that the server re-validates files and destination requirements, and that drafts may hold incomplete platform content. These are real behavioral bounds beyond the structured fields, though the closing note about drafts is only loosely tied to this tool's contract.

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?

The most important information — what it returns and that it must precede publish_post — is front-loaded in the first two sentences. It runs slightly long, and the trailing draft-incompleteness remark is the weakest sentence, but nothing is redundant with the schema or annotations.

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?

There is no output schema, and the description compensates by enumerating the limit categories returned. Combined with the ordering constraint, the per-platform cadence, and the validation caveat, an agent has everything needed to call this correctly and interpret the result before publishing.

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% and the single platform parameter already lists all valid slugs, so the schema carries the naming burden. The description still adds meaning by framing the call as per-destination-platform and by tying the returned limits to the post type being composed, which goes slightly beyond the schema baseline.

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 content limits for a platform") and immediately enumerates what those limits cover: max text length, media count, supported formats, file sizes, media specifications. This is clearly distinct from siblings like publish_post or list_media, so an agent can route without opening the 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 explicit when-to-use guidance ("Call this before publish_post when publishing or scheduling"), the correct cadence ("once for each distinct destination platform"), and how to apply results against the selected post type (feed, story, reel, carousel). An alternative is named and the ordering constraint relative to publishing is unambiguous.

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