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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds what the call reports (credits, plan, rate limit) and its intended role as a pre-batch check, which is genuine context beyond the annotations; it stops short of describing response structure or how exhausted credits manifest, but the definition is a no-parameter read.

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 sentences, zero filler, and the resource scope is stated before the usage advice. Every clause carries information an agent would act on.

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-only status check with no output schema, the description names the three returned data points and the situation that motivates the call. Missing only minor detail such as how a failed or unauthenticated check surfaces, which is acceptable at this complexity.

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 at the argument level. Baseline 4 applies.

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 gives a specific verb ("Check") plus the exact resource set: remaining credits, plan, and rate limit for the connected FetchMCP account. That is far more informative than the title alone and clearly separates it from the page-fetching sibling, though it never names that sibling directly.

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?

"Use before large batches of fetches" gives a concrete trigger condition for calling this tool. It offers no explicit when-not-to-use or alternative tool, but the guidance is clear enough to act on.

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