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

Beyond the annotations, the description discloses the key behavioral traits: the call only validates the request and charges nothing, it returns payment_url plus price and instructions, payment happens out-of-band via MPP/HTTP 402 with a Stripe shared payment token, and billing only occurs if the run passes its controls. That reconciles the readOnlyHint=true annotation with a paid product and warns that a failed control makes the run unsound.

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?

Front-loaded with what gets measured, then the payment mechanics, then the billing condition. It is dense but every sentence carries information; the opening sentence is long but reads as one coherent spec rather than padding.

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 carries the return-value burden and does explain both the immediate response (payment_url, price, instructions) and what a completed run yields (per-source shares by year, direction, agreement). Minor gap: it does not say what the failed-controls response looks like or how results are retrieved after payment.

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 coverage is 100%, so phrase, start, and end are already documented with bounds and defaults. The description adds only the framing that results are per-year, which the schema's year parameters already imply; it adds no new syntax or constraint detail beyond the schema.

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 states a specific verb+resource: measure one phrase across three named public sources (SEC EDGAR 10-K filers, Federal Register rules, USAspending obligations) year by year, with per-source controls, direction, and agreement. That scope distinguishes it cleanly from the single-source siblings run_filing_trend, run_regulatory_trend, and run_spend_trend.

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?

Usage is clear from the triangulation framing (pick this when you want all three sources compared at once rather than one trend tool), and the payment flow is spelled out. What is missing is an explicit exclusion sentence naming when a single-source sibling would be preferable, so the routing is implied rather than stated.

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