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

Annotations already declare a non-read-only, non-idempotent, destructive write, so the bar is lower, yet the description still adds auth requirements, the ordering constraint on age confirmation, the explicit statement that age cannot be inferred, and the fact that notes and dietary details are unsupported fields. It does not explain the destructiveHint=true flag for what reads like an additive operation, which is the one behavioral gap.

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?

The operation is front-loaded in the first clause, followed by tightly ordered constraints. Five sentences with essentially no filler, though the density makes it slightly heavy for a single-field-mapping create tool.

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?

Covers both input expectations (required vs optional fields, age eligibility) and output behavior ("results return the saved guest details"), despite there being no output schema. Auth requirements and unsupported fields are also disclosed, leaving nothing essential for a correct invocation unstated.

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 3 is the baseline, but the description adds real semantic meaning: it explains why age_band must be an explicit confirmation rather than something derived from names or relationships, and clarifies that phone/email are optional against required names. wedding_id is only loosely covered by "the selected wedding."

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 ("Adds a guest to the selected wedding") and pins the scope to the signed-in account's wedding, which cleanly separates it from update_my_guest and remove_my_guest. An agent can identify the operation without opening the 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?

Gives clear preconditions (explicit 13+ confirmation obtained before name/contact collection, sign-in plus Aisle membership) and states what input is required vs optional. It stops short of explicitly naming sibling alternatives such as update_my_guest or list_my_guests, so it is strong context rather than full routing guidance.

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