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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so safety is covered. The description adds real value beyond that by explaining the account/transaction-account/scenario hierarchy and the possibility of multiple child transaction accounts, which shapes how an agent interprets the result. It stops short of covering not-found behavior or auth requirements.

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?

Four tight sentences, front-loaded with the action and then the domain model. The mortgage-with-offset example earns its place by clarifying why multiple child transaction accounts appear, which prevents misinterpretation of the return value.

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?

There is no output schema, so the description's enumeration of returned fields (title, type, currency, balance, child transaction accounts and scenarios) fills that gap. Combined with annotations covering safety, an agent has everything needed for a one-parameter read.

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 id parameter is fully documented in the schema. The description adds no syntax, format, or lookup semantics beyond what the schema states, 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 a specific verb and resource ('Gets an account by its ID') and immediately defines the domain object, describing what an account contains (transaction accounts and scenarios). The 'by its ID' scoping makes it distinguishable from list_accounts without opening either schema.

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 single-record retrieval is implied by 'by its ID' and the required id parameter, but the description never explicitly says when to use this versus list_accounts or get_transaction_account, nor what happens if the ID is unknown. Usage is inferable but not guided.

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