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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds non-obvious context: this call does not authorize payment or any paid execution path, which is critical for an agent deciding whether a budget gate has been cleared. It stops short of describing the response shape or whether the estimate is illustrative vs. binding.

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 sentences, both front-loaded with the capability followed by the restriction. No filler and no restatement of the tool name or schema.

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 read-only planning tool with no output schema, the description covers what it does, its scope boundary, and the payment-related guarantee. It does not clarify that the returned estimate is planning-only/non-binding, which would fully close the loop.

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 five parameters including the two enums are already documented in the schema. The description adds no syntax, default, or interpretation detail beyond that, 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?

Names a specific verb ('Estimate ... Cost'), the exact resource (workflow-level budgeting via GET /v1/cost-estimate), and the scope limit ('planning tool ... for workflow-level budgeting only'). No sibling tool performs cost estimation, so the agent can place it immediately.

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?

Explicitly scopes usage ('for workflow-level budgeting only') and lists what it is not for (paid execution, payment, x402, wallet use, paid endpoint calls). No alternative tool is named, but none of the siblings competes for this purpose, so the gap is minimal.

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