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

Annotations already declare non-read-only, non-destructive, non-idempotent behavior, so the safety bar is lower. The description still adds non-obvious behavior beyond them: account numbers are masked in all output. It omits the duplicate-handling consequence implied by idempotentHint=false and any auth/permission 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?

Three short sentences with the verb and subject front-loaded and no padding; each sentence contributes something. Minor slack in 'for one of the user's TripLedger people,' which restates the personId concept.

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 five-parameter creation tool with no output schema and no schema descriptions, the description leaves too much unexplained: it never states whether accountNumber is required or auto-generated, what status defaults to, or what the tool returns. The masking note is helpful but does not fill the parameter 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?

With 0% schema description coverage across 5 parameters, the description must carry the whole load. It only clarifies personId ('one of the user's TripLedger people') and programId ('choose programId'); nickname, status, and accountNumber are left entirely undocumented, and it never says which fields are actually required despite the schema declaring none.

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 ('Create a loyalty account') and ties it to a domain object ('one of the user's TripLedger people'). It does not explicitly name its sibling update_loyalty_account, but the create-vs-update distinction is clear from the verb alone.

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?

Gives an explicit prerequisite and ordering: 'Use list_loyalty_programs first to choose programId.' That is real routing guidance an agent would otherwise miss. It stops short of saying when not to use it (e.g., account already exists) or naming update_loyalty_account as the alternative.

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