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

Annotations provide readOnlyHint=false, destructiveHint=false, idempotentHint=true, but the description adds critical behavioral context: it sends preferred times and a note, the landlord accepts or declines, and it does not book. It also mentions returning the message and thread, which is not in annotations. This goes beyond structured data and clarifies non-committal nature and follow-up capabilities.

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 with no fluff. The first sentence states the purpose clearly, the second explains the operation and constraints, and the third notes the return value. It is front-loaded and every sentence adds value, making it both concise and well-organized.

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?

Given the tool has no output schema, the description appropriately discloses the return value (message and thread). It covers the essential operational context: who it's for, what it sends, and what outcome to expect. Edge cases like authentication or error handling are not mentioned, but these are not critical given the tool's simplicity and the richness of the schema and annotations.

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%, so all four parameters are fully documented in the input schema. The description adds minimal extra meaning: it mentions 'up to three preferred times' and 'optional note,' which align with schema constraints, but provides no new syntax or format details. The baseline of 3 is appropriate since the schema carries the semantic weight.

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's purpose: 'Ask to tour a rental on A-du, as the signed-in person.' It specifies the verb (request/tour), the resource (rental), and the scope (signed-in person). It also distinguishes itself from booking tools by explicitly saying 'this does not book anything,' which separates it from siblings like start_application.

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 context on when to use the tool: to request a tour, not to book. The phrase 'this does not book anything' implies that for actual booking, another tool (e.g., start_application) is appropriate, but it does not name alternatives explicitly. The listing source is implied via schema (listing_id from search_rentals), but the description does not state exclusions or alternative tools directly.

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