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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so safety is covered. The description adds genuinely non-obvious behavior the annotations do not: returned amounts are bare numbers with no currency attached, plus the follow-up call needed to interpret them.

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?

Two short sentences, zero filler. The core purpose is front-loaded and the currency caveat follows immediately as supporting operational detail.

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 usefully compensates by disclosing the shape of the returned amounts and how to resolve currency. For a single-ID read tool with annotations covering safety, this is close to complete, though pagination/error behavior is not addressed (and is not really applicable here).

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% and the single 'id' parameter is fully documented (type, uuid format, pattern, description) in the schema. The description does not add any meaning about the ID beyond what the schema supplies, so the baseline 3 applies.

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 names a specific verb and resource ('Get a single project cost snapshot by ID'), and the word 'single' plus 'by ID' implicitly separates it from the sibling list_project_cost_snapshots. It stops short of naming that sibling explicitly, so it is clear but not maximally differentiated.

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?

It gives a concrete prerequisite: call get_organization_settings for currency_code before stating a currency. That is actionable when-guidance naming an alternative tool, though there are no when-not conditions or further routing between sibling get_* tools.

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