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

Beyond the readOnlyHint/openWorldHint annotations, it discloses the paid-call model ($0.002 USDC per successful call via x402 on Base, Solana or Arc) and that failed calls are not charged — genuinely decision-relevant for an agent. It stays consistent with readOnlyHint. It does not add rate limits or result-shape caveats, but the cost disclosure is a real value add over the 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?

Front-loaded with the registry and source before the field list and filters, then a separate sentence for pricing. The field enumeration is long but each item is substantive; slightly denser than necessary but no filler sentences.

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?

An output schema exists, annotations cover the read-only/open-world profile, and the schema documents every parameter, so the description need only supply sourcing, cost and sort semantics — which it does. The one missing piece is explicit sibling disambiguation between CAR and the other carbon registries.

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?

With 100% schema description coverage, the schema already documents all seven parameters including examples. The description only restates the filter dimensions (type, status, state, country, text) and adds one fact not in the schema — results are sorted by credits. Baseline 3 is appropriate when the schema carries the parameter detail.

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?

Specific verb+resource ('Carbon offset projects registered with the Climate Action Reserve') plus the upstream source (public APX project report) and an enumeration of returned fields. The explicit naming of CAR as the North American voluntary and California compliance registry implicitly separates it from energy_american_carbon_registry, energy_verra_vcs_registry and energy_gold_standard_credits.

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 makes the usage context clear — browse/filter CAR project records by type, status, state, country or text, sorted by credits. It does not explicitly state when to prefer this over the sibling registries (ACR/Verra/Gold Standard), so there is clear context but no exclusions.

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