track_cost_budget

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

Annotations are thin (readOnlyHint=false, idempotentHint=false, destructiveHint=false), so the description carries real weight. It discloses the critical behavioral trait: enforcement is server-side and blocking, refusing further tool calls until the budget is raised, and is 'not advisory.' That is exactly the kind of consequence an agent cannot get from annotations.

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, zero filler, and the enforcement consequence is front-loaded right after the core purpose. Every sentence earns its place.

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 need not be explained, and the behavioral consequence is well covered. However, the near-total absence of parameter semantics for a 5-parameter tool leaves a material gap for correct invocation.

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 only 20% (only session_budget_usd is documented). The description mentions no parameters at all, so session_id, prompt_tokens, completion_tokens and model_name remain undocumented in both places, leaving the agent without token-accounting guidance.

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 and resource: 'Book token spend against a session budget.' It is unambiguous and, since no sibling tool touches budgets, the agent can identify it immediately without needing sibling differentiation.

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 description implies the bookkeeping role and explains the consequence of exceeding budget, but never says explicitly when to invoke it (e.g., after each model call) or names any alternative or prerequisite. Usage is inferable rather than stated.

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