AI subscription stack cost

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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds useful provenance (dated official sources) and the estimation method (annual billing vs twelve-charge estimates), but much of the remaining text restates return fields that the output schema already carries.

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 front-loaded sentences: the primary action and the secondary capability come first, then returns, then the scoping exclusion. No filler sentences and no repetition.

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 an output schema present, the description need not explain return shape, and rich annotations cover safety. It supplies scope, provenance, and an explicit exclusion, leaving only the empty-list edge case and the required/minItems inconsistency unaddressed.

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 says nothing about planIds. The enum does list every valid plan ID, making the parameter largely self-documenting, but the description never clarifies the odd required-but-minItems-0 behavior (what an empty list returns).

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 action (total selected AI chat and coding subscriptions in USD) plus a secondary function (identify overlapping capabilities), and distinguishes itself from the sibling ai_api_cost by explicitly scoping out API token costs. An agent can identify the tool's job without opening the schema.

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?

Gives a clear use case ('reviewing a subscription stack') and an explicit exclusion ('not API token costs'), which effectively routes the agent away from ai_api_cost. It does not name the alternative tool directly, so it stops just short of full 5-level routing guidance.

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