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

With no annotations, the description carries full burden. It discloses the full scope of the return value, including fields, table clusters (core/reference), and call graph (calls/calledBy) parsed from program source. This goes beyond a generic lookup and gives agents a clear picture of what to expect, though it doesn't mention error conditions or explicitly state read-only behavior.

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 long sentence but well-structured with clear lists and parenthetical explanations. It packs substantial detail without wasted words, front-loading the core purpose. The length is justified by the need to enumerate the rich set of return fields, making it efficient despite its length.

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?

Since there is no output schema, the description must explain return values, and it does so thoroughly, listing every category of detail including name, system, database, class, GEMBASE program, help text, menu paths, table clusters, and call graph. This provides an agent with sufficient information to assess whether the result will meet a query's needs, making the description complete for its complexity.

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 parameter is already well-documented. The tool description adds only that it's 'by code', which isn't additional detail beyond the schema's 'Facility code, e.g. AP_A_002'. Baseline 3 is appropriate since the schema does the heavy lifting.

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 a specific verb ('lookup') and resource ('facility by code'), enumerating the detailed fields returned (name, system, database, class, etc.). It distinguishes itself from siblings like list_facilities and search_facilities by emphasizing 'Full detail for one ... facility by code' and listing unique aspects like call graph and table clusters.

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 conveys that this is for retrieving comprehensive details of a single facility when its exact code is known. It doesn't explicitly name alternatives or exclusions, but the contrast with list/search tools is implicit through the focus on one facility and 'by code'. This is clear context, though not exhaustive about when not to use it.

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