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

Annotations declare readOnlyHint=true and openWorldHint=true, which already signals a non-mutating, external-calling tool. The description adds genuinely useful context beyond that: the x402 payment cost ($0.05 USDC hosted vs $0.01 BYOK), that the API key is used once and never stored, that violations are auto-repaired, and the 'Never invents facts' constraint. It does not describe latency, rate limits, or failure modes when validation cannot be repaired.

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 the price and payment model front-loaded, then the capability summary. Every clause carries information, though the parenthetical pricing details sit before the core purpose, which is slightly backwards for an agent scanning for 'what does this do'.

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 18 parameters, no output schema, and a paid two-path (hosted vs BYOK) flow, the description does a fair job: it names the return payload (hooks, Fit Scores, share intents) and explains the payment challenge handshake. The gap is that nine input parameters remain unexplained and there is no output schema to fall back on.

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 50%, so half the 18 parameters (cta, goal, link, avoid, brand, voice, audience, language, hasMedia) are undocumented in both schema and description. The description does add meaning for the BYOK path (api_key, provider, model map to the '$0.01 with your own provider key' tier) and confirms the up-to-14 platform default. That partially compensates but falls short of the majority-undocumented surface.

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 names a specific verb+resource: rewrites one post into native versions for up to 14 platforms, validates every variant, auto-repairs violations, and returns hooks, Fit Scores and share intents. That is far more than a tautology. It does not, however, explicitly contrast itself with the closely overlapping sibling omnipost_validate (which also validates variants), so sibling differentiation is only implicit.

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?

Pricing tiers and the instruction that omitting payment_signature yields the payment challenge give real usage context. But there is no statement of when to choose this over omnipost_validate, omnipost_publish, or omnipost_share_intents, so the routing decision is left to inference.

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