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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered. The description adds value beyond that by disclosing what is actually returned (install rules, validity start, notes) in the absence of an output schema, plus the instruction to surface notes to the buyer — genuinely non-obvious behavior.

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?

One dense sentence front-loads the return contents, and a second short imperative delivers the workflow constraint. No filler, no restatement of the title, and the most decision-relevant information (what you get back) comes first.

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 single-read tool with full annotation coverage and no output schema, the description compensates well by enumerating returned fields and flagging the notes-reading obligation. Only minor gaps remain, such as error behavior for a stale or invalid plan_id.

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?

With one required parameter at 100% schema coverage, the schema already documents plan_id including its origin ('plan_id from list_plans'). The description adds nothing about the parameter's format, validity, or what happens with an unknown id, so this sits at the baseline.

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 verb-and-resource pair (full details of one plan) and enumerates the exact contents returned: countries, data, days, phone number, install rules, validity start, notes. That is far more precise than the title 'Get plan'. It implies but never explicitly names the list_plans counterpart for the collection-vs-single distinction.

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 a concrete workflow rule — read the notes to the person before create_order — which anchors the tool in the order flow and tells the agent this is a pre-purchase inspection step. It stops short of an explicit exclusion such as 'use list_plans to browse candidates first', so the routing is clear but not complete.

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