Disco

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

Annotations indicate destructiveHint=true and idempotentHint=false, but the description adds valuable context beyond this: it specifies the cost ($0.10 per credit, $10 per pack), clarifies that credits are used for private analyses (with public ones free), and mentions the optional API key with environment variable fallback. This enriches understanding without contradicting 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?

The description is well-structured and front-loaded with the core purpose, followed by pricing details, usage context, prerequisites, and parameter explanations. Every sentence adds value—no fluff or repetition—making it efficient and easy for an agent to parse quickly.

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?

Given the tool's complexity (a purchase operation with financial implications), the description is complete: it covers purpose, pricing, usage context, prerequisites, and parameters. With an output schema present, return values need not be explained, and annotations handle destructive/idempotent hints, so no gaps remain for effective agent use.

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. It effectively explains both parameters: 'packs' is defined as 'Number of 100-credit packs to purchase' with a default, and 'api_key' is clarified as optional with an env var alternative. This adds essential meaning beyond the bare schema, though it could note data types or constraints more explicitly.

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 clearly states the specific action ('Purchase Disco credit packs') and resource ('using a stored payment method'), distinguishing it from siblings like discovery_add_payment_method (which sets up payment) and discovery_analyze (which uses credits). It specifies the purpose is for buying credits, not other account actions.

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?

It explicitly states when to use this tool ('Purchase Disco credit packs') and provides clear prerequisites ('Requires a payment method on file — use discovery_add_payment_method first'). It also distinguishes usage context by noting credits are for private analyses (public ones are free), guiding the agent away from unnecessary purchases.

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