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

Annotations already indicate readOnlyHint true and destructiveHint false, covering safety expectations. The description adds no extra behavioral details beyond the basic operation (e.g., return format, not-found behavior, or company requirement), but the annotations remove the need to re-state safety. Overall the tension is present but low-risk due to the read-only annotation.

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 entire description is one concise sentence with no fluff. It puts the core action first and contains a clear ID for scoping, maximizing readability with minimum words.

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?

Combined with a fully descriptive schema, annotations, and the clear read-only nature from the sibling set, the description supplies enough to call the tool correctly. While there is no output schema and the description doesn't explain return values, that information is not critical for a direct get-by-id invocation and is largely implicit from the tool's name. The connectionRef behavior is well handling in the schema description.

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?

Input schema covers 100% of parameters with descriptive text, including companyName and connectionRef details. The description itself does not add parameter information beyond identifying id be the lookup key, so by default the schema carries semantics. The parameter details are complete; describing them in the text is not required given the schema's coverage.

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 uses a specific verb ('Gets'), names the resource ('brc_purchase'), and scopes it by 'by id'. This makes it immediately distinct from batch, list, create, and update tools in the sibling set.

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 implies usage when you already have a purchase id, but it does not explicitly state when to choose this tool over alternatives for non-read operations. There is no mention of exclusions or a preferred alternative (e.g., when to use a list or search instead). The 'by id' phrasing gives minimal context but not explicit guidance.

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