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

Annotations already declare readOnly, idempotent and non-destructive, so safety is covered. The description adds genuine context beyond them: prices are intentionally omitted, unknown values are dropped rather than fabricated, and the call costs roughly 50 tokens. That last point in particular is not derivable from any structured field.

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?

Labelled Purpose/When/Cost lines make the entry points scannable and front-load the verb. Every sentence carries information, though the 'prices are on the pricing page' clause is slightly redundant with the 'Cost' label's different sense of the word 'cost', which may momentarily confuse.

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?

An output schema exists, so return values need no explanation, and the description covers scope, exclusions and invocation cost. For a zero-parameter, annotated, read-only tool this is close to fully sufficient; only an explicit note on sibling relationship (e.g. when to prefer subscription_links) is missing.

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 and the baseline is 4. The description correctly spends no words on parameters and instead uses the space for scope and cost.

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 Purpose line names a specific verb and resource ('Read the user's searchnapply subscription') and enumerates what is returned: daily call limit and today's usage. It also carves out what is not returned (price), which sharpens the boundary. It does not name the sibling subscription_links, so it stops short of a 5.

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 'When' clause gives three concrete user-intent triggers (cost, trial end, tool stopped answering), which is strong routing guidance. It redirects pricing questions to the pricing page rather than to a sibling tool, and it never explicitly excludes a sibling or names an alternative call, so it is clear but not exhaustive.

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