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

readOnlyHint=true already establishes the safe-read profile, so the description's only added content is naming the returned fields. It discloses nothing about auth requirements, whether the account is implicit from credentials, or how credits are denominated.

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?

It is a single short fragment with no filler, but it is under-specified rather than concise — there is no lead verb or scope statement to front-load. Brevity here costs clarity.

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 no output schema, the description is the only place return values can be described, and it names only two fields (plan, credits) without structure or units. It is adequate to pick the tool but thin for interpreting the result.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The absence of inputs is consistent with an implicit 'current account' read.

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 fragment identifies the resource content ('plan and available credits') but omits a verb, leaving the agent to infer that this is a retrieval of the caller's account info. Siblings are all video-scoped, so there is no ambiguity to resolve, but the purpose statement is a noun phrase rather than a clear action.

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?

No guidance on when to call this versus other tools, no mention of prerequisites such as authentication or which account is being read. The agent must guess that this returns the calling account's own state.

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