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

Annotations already declare readOnlyHint=true and no I/O, so the safety profile is covered. The description adds real value beyond annotations: it discloses the pricing formula (base 23, -5 for excluding ai-ugc, +3 for server-side render) and confirms no credits are spent, which is behavior not visible in the schema or annotations.

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 short sentences, front-loaded with the purpose and effect, then the formula, then the safety note. No filler; every clause carries meaning.

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?

An output schema exists, so return-value explanation is not required. The description covers purpose, cost semantics, and safety. It could be slightly richer by noting what the estimate returns (a credit number) or the baseline assumptions, but for a 2-param read-only estimator it is complete enough to invoke correctly.

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 compensate – and it does, mapping 'exclude' to the -5 credit delta for 'ai-ugc' and 'render' to the +3 server-side render surcharge. It does not explain the full enum list, but the critical cost-affecting semantics are conveyed.

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 (estimate) plus the resource (credit cost of snack generation) and the key distinction 'BEFORE running it' – which routes it cleanly away from generate_snacks, generate_influencer_snack, and get_credits. An agent can immediately tell this is a dry-run cost estimator, not a generator.

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?

'BEFORE running it' clearly frames the when-to-use context, and the no-I/O/no-cost note reinforces it as a pre-flight check. However, it never names sibling alternatives (generate_snacks, get_credits) so an agent must infer the routing itself.

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