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

With no annotations, the description carries the full behavioral burden. It implies a non-mutating introspection of the connected key's quota, which signals a safe read, but it does not confirm read-only semantics, state what happens with an invalid or expired key, or indicate whether results are cached or live.

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?

A single short sentence with no filler, and the key concept (plan and credits) is front-loaded. The phrasing "credits left" is slightly informal but costs nothing in length.

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?

For a zero-parameter read tool this is close to adequate, but with no output schema the description is the only guide to the return payload, and "plan and credits left" omits units, currency, expiry/reset timing, and whether limits are per-key or per-account.

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 no parameter semantics to explain and the schema itself is complete. The description correctly adds no parameter talk, matching the empty input object.

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?

"Plan and credits left for the connected key" names the resource content being reported, so an agent can infer this returns billing/quota status. But it is a noun phrase with no verb (get/read/retrieve) and never says it returns a status object for the currently authenticated key, leaving the purpose only implied.

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?

There is no when-to-use guidance, no prerequisites, and no routing versus the siblings (create_account, list_templates, render_image). An agent must guess whether this is for pre-flight quota checks, post-failure diagnosis, or account setup.

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