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

Annotations already declare readOnly=false, idempotent=true, and destructive=false. The description adds meaningful extra semantics: 'null clears it' defines the null behavior for budget, and 'Only the fields given are changed' discloses partial-update behavior that the annotations do not convey.

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?

A single front-loaded sentence with a parenthetical that earns its place by clarifying null handling. No filler or redundancy.

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?

The tool is small (3 parameters, no output schema) and annotations cover safety and idempotency. The description covers the essential update semantics (partial update, null clearing); only edge cases like invalid person_id or empty update payloads are left unstated, which is reasonable for this complexity.

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 only 33%, with budget described but name and person_id undocumented in the schema. The description partially compensates by explaining that null clears the budget and that unspecified fields remain unchanged, but it does not add meaning for person_id or the rename semantics beyond the obvious.

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: renaming a person or changing their budget on the signed-in person's gift list. The scope (gift list, not generic person) and the two mutable fields make it distinguishable from update_gift and add_person, though it doesn't explicitly name an alternative.

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 'renames a person ... or changes their budget', but there is no explicit when-to-use or when-not-to-use guidance, and no mention of prerequisites such as the person already being on the list.

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