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

Annotations already say non-readonly, non-idempotent, non-destructive; the description adds substantive behavior beyond that: a per-account redemption limit, a first-days eligibility window, and a staged grant model where the response separates 'granted' from 'missing'. It does not say what happens on an invalid or already-redeemed code, which is the main remaining 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?

Front-loaded with the action, then eligibility, then the response shape, then the follow-up — a sensible ordering with little waste. The 'exactly like POST /v1/gift-codes/redeem' clause is redundant for an MCP caller and slightly bloats an otherwise tight paragraph.

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?

Output schema exists, so return values need not be explained, yet the description still summarizes the staged 'granted'/'missing' structure that matters for deciding the next call. Combined with the eligibility limit and the gift_code_pack handoff, an agent has everything needed to invoke and follow up correctly.

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?

Only one parameter and schema coverage is 100%, so the schema fully documents 'code'. The description adds a light hint about code provenance ('giveaway site or newsletter') but no format or validation detail. Baseline 3 is right when the schema carries the meaning.

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?

Names a specific verb and resource ('Redeem a gift code') and scopes the source ('handed out by a giveaway site or a newsletter'), which separates it from generic code-entry work. It does not distinguish itself from the close sibling redeem_coupon, so an agent may still hesitate between the two.

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 real eligibility context: 'One pack per account, only in an account's first days.' It also routes the follow-up explicitly ('Call gift_code_pack later to collect a stage that has come due'), which is a genuine when-to-call-next instruction. Missing only an explicit contrast with redeem_coupon.

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