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

With no annotations, the description carries the full burden and does so richly: human-gated elicitation at the highest tier, typed form values overriding the arguments, Stripe price immutability, minting a new price while leaving the old object intact, existing subscribers retaining their price, and one_time switching clearing monthly/yearly price ids.

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?

Long but front-loaded with the core purpose, then constraints, then edge cases and follow-up. Nearly every sentence adds operational value, though the density is near the upper limit for a three-parameter tool.

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 mutation tool with no annotations, no output schema and 0% schema description coverage, the description is unusually complete: it covers authorization, override semantics, immutability outcomes, subscriber impact, refusal cases and a required follow-up sync step.

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 0%, so the description must compensate, and it largely does: it maps tier, amount_cents, payment_type (one_time vs subscription) and monthly_amount_cents to their meaning and notes that arguments only pre-fill the proposal. It does not explain app_id or clarify amount units (cents) beyond the schema's naming.

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 ('Change what an app's EXISTING tiers charge') and enumerates the mutable dimensions (amount, billing model). It is clearly distinguishable from siblings like update_plan_limits and update_plan_meta, which touch different aspects of a plan.

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 names prerequisites and routing ('Use list_plans first for tier slugs and current amounts'), the post-step (run plans:sync), and the exclusion set (free, contact and payg tiers are refused because that is a catalog change, not a reprice). It also states when the tool will not work at all (non-elicitation clients, unless dry_run).

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