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 annotation carries the safety profile. The description adds the underlying API mapping (GET /subscriptions/{subscription_id}), but says nothing about behavior on an unknown id, cancellation status, or response shape.

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 sentences, front-loaded with the action and resource, with the endpoint as compact supplementary context. No wasted words.

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 one-parameter read tool with readOnlyHint covering safety and 100% schema coverage, the description is sufficient to invoke correctly. The only gap is sibling disambiguation against the other subscription sub-resource getters, which the description does not address.

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% and the only parameter (subscription_id) is fully documented in the schema. The description's 'by id' merely restates what the schema already defines, adding no format, prefix, or validation detail. 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 (Fetch) and resource (a single subscription by id), which clearly distinguishes a single-record read from orb_list_subscriptions. It does not, however, name or differentiate itself from the other subscription-scoped readers (orb_get_subscription_costs, orb_get_subscription_schedule, orb_get_subscription_usage).

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 implied by 'Fetch a single subscription by id' – the agent can infer this is the tool for retrieving one subscription when the id is known. There is no explicit when-to-use guidance, no exclusion, and no routing to siblings such as orb_list_subscriptions or the costs/schedule/usage variants.

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