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

Annotations cover readOnlyHint, openWorldHint, idempotentHint and destructiveHint, so safety is partly declared. The description adds real behavioral context beyond that: the app handles sign-in, missing-profile and phone-check feedback comes back in the result, and documents are not sent in chat but shared on the Heimster application page. It stops short of describing rate limits or what the result payload looks like.

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?

Front-loaded with purpose and a direct call-to-action, then handles edge cases and the document policy in order. The parenthetical multilingual keywords are somewhat noisy but the rest is efficient.

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 3-parameter mutation tool with no output schema, the description covers the confirm gate, auth handling, profile preconditions, result feedback and a policy on document sharing. It lacks any mention of return shape or failure semantics, which keeps it from a 5.

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 67%, so the schema already documents the optional message and language fields. The description adds no syntax or format detail for listing_id or language beyond the enum already present, so baseline 3 is appropriate.

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?

Specific verb (apply) plus resource (RENTAL listing) with multilingual keywords that aid retrieval. It is clearly distinguishable from register_purchase_interest, send_enquiry, and owner_enquiry.

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?

Explicitly says to call it directly once the user confirms and explains the not-signed-in and missing-profile/phone-check branches, so the agent knows when not to intervene. It does not compare against sibling alternatives like owner_enquiry or send_enquiry, but the condition for use is clear.

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