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

readOnlyHint=true already tells the agent this is a safe, non-mutating read, so the bar is lower. The description adds the upstream endpoint mapping (GET /v1/subscriptions/), which is mildly useful for debugging, but says nothing about pagination defaults, result caps, or rate limits beyond what the schema implies.

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, no filler, with the capability statement front-loaded before the endpoint reference. Every clause earns its place.

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 read-only list tool with full schema coverage and a clear readOnlyHint annotation, the description covers purpose and filter scope adequately; return values need not be described since no output schema is expected. Minor gap: no guidance on combining filters or pagination behavior.

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 100%, so every one of the 8 parameters is already documented in the schema with its meaning. The description's filter list mirrors the schema rather than adding semantics such as accepted status values, id formats, or organization_id scoping rules. Baseline 3 applies when the schema carries the load.

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 states a specific verb and resource ('List subscriptions') and enumerates the filter dimensions (customer, product, status, active state, cancellation window), so an agent knows exactly what the call returns. It does not explicitly distinguish itself from polar_get_subscription or the other polar_list_* tools, which is the only thing keeping it from 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 enumerated filters imply the usage context (bulk retrieval with narrowing criteria), but there is no explicit when-to-use guidance, no mention of the singular polar_get_subscription alternative, and no note on pagination strategy. Usage must be inferred rather than read.

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