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

The description discloses that results include 'dated source context' and that 'source_file and snapshot_digest are nullable when no single retained snapshot represents the response.' Since annotations already declare readOnlyHint=true, this additional edge-case behavior about nullable fields is valuable and goes beyond the annotation, helping the agent handle incomplete responses without contradicting the read-only nature.

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 two sentences, front-loaded with the core action and sources, followed by return behavior and use cases. Every clause carries weight; there is no redundancy, and the structure allows quick parsing by an AI agent.

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?

With no output schema, the description adequately covers the essential return semantics ('dated source context', nullable 'source_file' and 'snapshot_digest') and gives clear use cases. Given the simple 2-parameter schema and read-only annotation, this is nearly complete. A brief note pointing to the history sibling for past records would make it fully complete, but it is already strong.

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%, with both parameters fully described (character lengths and mutual exclusivity). The tool description only restates 'by UEI or CAGE' and adds no new parameter-level meaning. It stays at the baseline for high schema coverage, as the description does not compensate for missing info or add examples beyond the schema.

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 opens with a specific verb and resource: 'Look up a US federal contractor by UEI or CAGE' and names concrete data sources (SAM.gov, USASpending, FAPIIS, FAR 4.18). This clearly defines the tool's scope and differentiates it from siblings like history or sanctions, as it focuses on current contractor records across these sources.

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?

It explicitly states the intended use: 'Use for contractor identity, registration, award, responsibility, or ownership due diligence.' This gives clear context for when to apply the tool, though it does not explicitly name alternatives or state when not to use it. The mention of 'available records' implies current lookup versus historical, but a direct sibling reference would strengthen this.

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