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

With no annotations, the description carries the full burden. It discloses key behavioral aspects: returns changes relative to historical baselines, identifies accelerating ports, and flags ports approaching critical thresholds. It adds context beyond the tool name by describing output contents. It does not mention data freshness, update frequency, or limitations, but for a read-only analytical tool with no parameters, the description is reasonably transparent.

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?

The description is three sentences, each earning its place: the first states the core function, the second details what it returns, and the third gives user context. It is front-loaded with the primary purpose and contains no filler. The structure is clear and scannable.

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 no-parameter tool with no output schema, the description is quite complete. It explains the analytical value, key outputs, and use cases. It could possibly detail the exact format of trends or thresholds, but the description provides sufficient contextual information for an agent to understand its purpose and 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?

The tool has zero parameters, so schema coverage is 100% by default. The description contributes no parameter-specific semantics because there are none to explain. Per the rubric, a 0-parameter tool gets a baseline of 4, and the description does not introduce any confusing or unstated parameters.

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 the tool as providing port congestion trend analysis, not just current congestion, with a specific verb ('Get') and resource ('port congestion trend analysis'). It distinguishes from siblings by emphasizing 'direction and trajectory' and answering 'Which ports are getting worse and how fast?' The comparison to 'not just current congestion' explicitly differentiates it from likely sibling port_congestion_monitor.

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 provides clear use cases: 'Used by logistics planners to reroute shipments before congestion peaks, and by importers to anticipate lead time extensions.' This implies when to use the tool (forward-looking trend analysis). However, it does not explicitly name alternatives or state when not to use it, though the 'not just current congestion' phrase hints at alternative current-state tools.

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