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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so safety is covered. The description goes beyond them by disclosing the shape of the result: original official-event quotations plus retention months, payout timing, and caution conditions. That is valuable output-content context, though it omits any note on result size or ordering.

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 dense sentence front-loads the core concept (plans that net positive) before the supplementary detail about quoted event text and conditions. It is well-structured, though the run-on length makes it slightly heavy for one sentence.

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?

With no output schema, the description compensates by explaining what the result contains (event quotes, retention months, payout timing, cautions), and annotations cover the safety profile. The gap is that it never clarifies the boundary against the many pricing siblings, which is the main thing an agent still needs.

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 description coverage is 100% (mno enum, brand substring, limit 1~50 default 25, minNet, excludeReferral), so the schema already carries parameter meaning. The description adds nothing about how these filters interact or what defaults apply, so baseline 3 is correct.

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?

The description states a specific resource and concept: a table of MVNO plans where event gifts (Naver Pay, vouchers, points) exceed the retention-period monthly fee plus SIM cost, i.e. plans that net positive. That is far more specific than a generic 'list plans' tool. However, it never distinguishes itself from pricing siblings like cheapest_by_data, price_index, or search_plans, so an agent must infer the boundary.

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 only implied: the tool is for finding plans where gifts outweigh costs. There is no explicit 'use this when…' statement, no exclusions, and no named alternative for related questions (e.g. plain cheapest price lookups), so the agent has to infer when this beats the price-focused siblings.

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