get_vessel_position

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

With no annotations, the description must disclose behavioral traits. It mentions satellite fallback is charged per call (via the 'sat' parameter), which is useful, but it doesn't disclose the default behavior (e.g., what happens if no terrestrial position exists without sat=true? Does it return null or error?). It also doesn't mention data freshness or potential delays. The description adds minimal behavioral context beyond the 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?

The description is a single concise sentence that front-loads the purpose. Zero waste, effectively communicates the core function. The schema handles parameter details.

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?

This is a moderately simple read operation with no output schema and full schema parameter coverage. The description covers the return value but doesn't discuss edge cases (e.g., no position available, satellite fallback behavior) or whether it's a direct lookup vs. historical. With no annotations, it could benefit from a note on default behavior, but it's adequate for basic selection.

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 100%, so the schema already explains all parameters. The description adds value by explicitly listing the returned fields (latitude, longitude, speed, heading), which helps agents understand the output. The 'sat' parameter guidance about prepaid balance is also valuable. Baseline 3, plus extra context, justifies 4.

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 states the tool returns current position data (latitude, longitude, speed, heading) for a specific vessel. It distinguishes from siblings like get_vessel (general info) and get_vessel_eta (estimated arrival), though it doesn't explicitly name alternatives.

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 schema's 'sat' parameter includes guidance on when to use satellite fallback (only when stored position is insufficient), which implies usage context. However, the description itself doesn't specify when to use this tool versus alternative position tools like get_vessel_positions_batch or get_vessels_in_area. The description lacks explicit exclusions.

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