estimate_cost

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

No annotations are present, so the description must carry the behavioral disclosure burden. It explains scope ('under the current config'), the kind of estimate provided, and the conditional pricing behavior on metered backends. Still, it does not explicitly state whether the operation is read-only, what side effects it has, or how precise the estimate is.

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 with no filler. The key action, output content, conditional behavior, and usage instruction are all front-loaded and clearly expressed.

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 params, no annotations, and no output schema, the description covers the essential inputs ('current config'), outputs (calls/tokens/duration/price), and timing ('before session_start'). It is slightly ambiguous what 'current config' refers to, but it is adequate for this tool's simplicity.

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?

The tool has zero parameters, so there is no schema coverage gap to compensate for. The description adds meaning by explaining that the estimate is based on 'the current config' and what is being measured.

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 clearly identifies a specific verb-like action ('Pre-flight size of a session') and details exactly what it produces: calls, tokens per agent, duration, and price on metered backends. It also distinguishes itself from siblings by explicitly framing it as a pre-`session_start` step.

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 explicit guidance on when to use the tool: 'Run this before session_start and show the user.' However, it does not mention when not to use it or name alternatives from the sibling list, so it stops short of full exclusion guidance.

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