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

Annotations establish read-only/safe-execution context, and the description adds meaningful behavioral facts beyond them: prices are Google Cloud list prices, sizing is derived from real runs' machines and run times, key services are included, and the output is explicitly an estimate rather than a quote. It stops short of disclosing currency or whether discounts/actual billing are reflected.

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?

Three short sentences, front-loaded with the core action and scope, followed by the crucial caveat that this is an estimate. Every sentence contributes distinct information with no filler.

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 cost estimator with no output schema, the description should clarify what comes back (a cost breakdown? currency? per-service line items?) and whether historical or hypothetical inputs are used. It covers the pricing basis and estimate caveat well but leaves the return value opaque, which is a notable gap given the absence of an output schema.

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%, so all four parameters, including the enum values and defaults, are already fully documented in the schema. The description mentions 'key services' in prose but adds no new syntax, units, or interpretation beyond what the schema provides; 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?

States a specific verb (estimate) and resource (cost of Federated Computing runs) with clear scope: cloud time at Google Cloud list prices for observed machine/run configurations plus key services. It is unmistakably different from the doc/list siblings, but it never names or explicitly contrasts with any sibling, which is the rubric's bar for 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?

The phrases 'same numbers as the cost estimator page' and 'an estimate, not a quote' imply how to present the result, but there is no explicit guidance on when to call this versus other tools or for which planning scenarios (pre-provisioning, budgeting) it is intended. Usage is inferred rather than stated.

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