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

Annotations already declare readOnly, idempotent, non-destructive, and open-world behavior, so the safety profile is fully covered. The description adds only the REST endpoint path; it says nothing about auth requirements, behavior on an unknown token, or what the response contains. With annotations carrying the load, a 3 is fair.

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 short, front-loaded sentences with no filler. However, the second sentence ('GET /subscriptions/{token}') largely restates the first, so a small amount of the text does not earn 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?

A simple one-parameter getter whose schema and annotations are complete, so little is required. Still, with no output schema, the description gives no indication of what the returned subscription object contains, which is the main remaining gap.

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 coverage is 100% and the single parameter is documented with an example token in the schema itself. The description's '(sub_...)' hint merely restates that, adding no new syntax or format information. Baseline 3 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?

States a specific verb+resource ('One subscription by token') and names the token prefix, which cleanly separates it from list_subscriptions and get_subscription_ledger. It doesn't explicitly contrast with those siblings, 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?

Usage is only implied: fetch a single subscription when you already hold a token. There is no explicit 'use list_subscriptions to find a token first' or any statement about when not to call it.

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