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

Annotations only declare readOnlyHint and openWorldHint; the description goes well beyond by disclosing the data provenance (AIS-derived PortWatch), a freshness caveat ('the latest date lags real time'), and the billing model ($0.002 USDC per successful call via x402 on Base/Solana/Arc, failed calls not charged). The lag warning and the charge-on-success rule are exactly the operational facts an agent cannot get from annotations or schema.

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?

Three dense sentences, front-loaded with what the tool returns and immediately followed by the caveat and the sibling pointer. The connector phrase 'Related tools on this server, for a different need:' is slightly clunky, but no sentence is filler and the pricing note is kept to the end where it belongs.

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 one-parameter, read-only lookup with a declared output schema, the description supplies everything the agent needs: subject, source, granularity, freshness limitation, cost, and the nearest alternative. Return values need not be explained because the output schema covers them, so nothing material is missing.

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% and the single 'days' parameter (1–30, default 7) is fully documented in the schema, so the description carries no extra burden and the baseline 3 applies. The description adds nothing about the units or relationship of 'days' to the reported lag, which would have been a marginal improvement.

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 — 'Daily vessel transits through the Malacca Strait chokepoint, counted by ship type with capacity' — plus the upstream source (IMF PortWatch, AIS-derived). It also explicitly separates itself from the Panama Canal sibling and from VTS telemetry, so an agent can place it among the many logistics tools without opening a schema.

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?

Names the alternative explicitly and the condition that selects it ('logistics_panama_canal_transits when you need daily vessel transits through the Panama Canal chokepoint'), and adds a negative qualifier ('Not VTS telemetry; transit counts only'). It stops short of stating when this tool should NOT be used for a Malacca-specific need (e.g. vessel-level tracking via logistics_vessel_tracker), so the routing is only half-complete.

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