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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so 'Read only' merely restates structured data. The description adds value by naming the returned fields, partially compensating for the absence of an output schema, but says nothing about not-found behavior.

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?

Eight words, no filler, return fields front-loaded. Slightly telegraphic ('One subscription:' as a fragment) and 'Read only' duplicates the annotations, costing a little precision.

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 single-parameter read tool with full schema coverage, the field enumeration substitutes adequately for the missing output schema. Only the handling of a nonexistent subscription id is left unspecified.

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?

One parameter with 100% schema description coverage, where the schema itself explains it is an id from list_subscriptions. The description contributes no additional parameter meaning, so the baseline of 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 the resource ('one subscription') and enumerates what it returns (plan, price, period, next charge, signature), which distinguishes it from the list_* siblings. The retrieval verb is only implicit in the title ('See') rather than in the description itself.

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?

No when-to-use guidance: nothing tells the agent to pick this over list_subscriptions or list_student_subscriptions, nor what to do when the ID is unknown. The only routing hint ('Id from list_subscriptions') lives in the schema, not the description.

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