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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds valuable behavioral context: default output lists all platforms compactly, naming platforms expands to sizes, durations, options, and quirks, and full detail is several times larger.

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?

Three sentences with no filler: the core purpose is front-loaded, followed by parameter behavior, then the recommended usage moment. Every sentence earns its place.

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 an output schema present and annotations covering safety, the description supplies all necessary operational context: default behavior, optional parameter effect, and when to use the tool. Nothing an agent needs to invoke it correctly is missing.

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 platforms parameter is already documented. The description goes beyond the schema by explaining the behavioral effect of omitting it versus naming specific platforms, including the response-size tradeoff.

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?

Description states exactly what the tool does: list what each platform accepts, including media kinds, counts, and caption limit, with optional expanded details. It is clearly distinguishable from sibling tools by focusing on platform rules rather than accounts, groups, media, or posts.

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?

Explicitly advises reading this before scheduling rather than discovering the rules by being rejected. It also explains how to control response size by naming only relevant platforms. It does not explicitly name alternatives, but the usage context is clear and there is no competing platform-rules tool among siblings.

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