Disco

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

Annotations provide destructiveHint=true (indicating a state-changing operation) and idempotentHint=true (safe to retry). The description adds valuable context beyond this: it specifies that paid plans require a payment method, credits roll over on paid plans, and the api_key can be omitted if set via environment variable. This clarifies authentication needs and billing implications.

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 plan details and parameter explanations. Every sentence earns its place by providing critical information without redundancy, making it efficient and easy to parse.

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 (subscription management with billing implications), the description is complete. It covers purpose, plans, requirements, and parameters. With annotations covering safety aspects and an output schema present (though not detailed here), no significant gaps remain for agent usage.

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 fully compensates by explaining both parameters. It defines the 'plan' parameter with specific tier IDs and their details (names, prices, credits), and clarifies that 'api_key' is optional if DISCOVERY_API_KEY is set. This adds essential meaning not in the schema.

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 tool's purpose: 'Subscribe to or change your Disco plan.' It specifies the verb ('Subscribe to or change') and resource ('Disco plan'), and distinguishes it from sibling tools like discovery_list_plans (which lists plans) or discovery_add_payment_method (which handles payment setup).

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?

The description provides clear context for when to use this tool by listing available plans and noting that paid plans require a payment method. It implies usage for subscription management but doesn't explicitly state when not to use it or name alternatives like discovery_purchase_credits for credit top-ups without plan changes.

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