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

Annotations already declare this is a non-readOnly, non-destructive, non-idempotent write. The description earns credit beyond that by disclosing a plan-based quota (3 branches on Free) and the time-zone fallback behavior, both of which affect whether and how the agent should call it. It does not say what is returned or what error surfaces when the quota is hit.

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, zero filler, with the core action front-loaded and constraints following in priority order. Nothing repeats the schema verbatim.

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 two-parameter creation tool with full schema documentation and no output schema, the description covers what is needed: what is created, the quota constraint, and the default resolution for the optional field. Return shape is out of scope given no output schema exists.

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%, so the baseline is 3, but the description adds a genuinely new semantic: omitting time_zone causes the shop's time zone to be inherited. That defaulting rule is not in the schema and directly changes how an agent should construct the call. The uniqueness constraint on name is left to the schema.

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 pair ('Adds a branch') and even defines the domain concept ('a location where stamps are given') plus the parent entity (shop). It implicitly contrasts with update_branch and list_branches in the sibling set, though it does not name them.

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 description supplies a real precondition — the Free plan caps the shop at 3 branches — which tells the agent when the call may fail. It stops short of naming update_branch as the alternative for existing locations or stating any order-of-operations guidance.

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