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

Annotations already declare readOnlyHint, idempotentHint and non-destructive, so safety is covered. The description adds genuinely useful behavioral context beyond that: the output is ordered cheapest-region-first and spans Linux/Windows plus 1/3-year reservation and savings-plan pricing, which tells the agent what shape of data to expect.

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-loaded with the resource and followed by the output scope. Every clause earns its place, though the parenthetical price enumeration is long enough to slightly slow the read.

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 an output schema present, return values needn't be described, yet the description still usefully previews the price dimensions and ordering. Combined with full schema coverage and complete annotations, an agent has everything needed to invoke it 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?

Schema description coverage is 100% (both size and region are documented with examples), so the baseline is 3. The description's 'per region' phrasing hints that region narrows prices but adds no syntax or default behavior beyond the schema.

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+resource ('Specs of one Azure VM size') and scopes it to a single size, which implicitly contrasts with the listing sibling find_vm_sizes. However, it never names a sibling or explicitly distinguishes itself from estimate_vm_cost, so it falls short of a 5.

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: an agent can infer this is for detailed single-size lookup, but there is no explicit 'use this when...' statement and no mention of when to prefer estimate_vm_cost or find_vm_sizes instead. Adequate but with a clear gap.

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