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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuinely useful behavior: the window runs from the start date to now, listings published after the start date clamp to their publish date, and a Cotlet API key with app access is required. It does not mention rate limits or pagination, but the added context is substantial.

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?

Four short sentences, front-loaded with purpose and scope. The second sentence ('Returns the performance numbers PF Expert shows for one listing') slightly restates the first ('Views and leads for one listing'), a minor redundancy, but nothing else is wasted.

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 single-listing read tool with no output schema, the description covers what is returned at a conceptual level, the time-window semantics, volume guidance, and the auth prerequisite. It stops short of describing the shape of the returned metrics, which is the main remaining gap.

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 the baseline is 3; the description earns a bump by explaining the semantics of 'since' beyond the schema's 'Count from this date' — the window extends to now and late-published listings count from their publish date. It confirms listing_id provenance ('filter with list_listings first') rather than adding new detail there.

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?

States a specific resource ('one listing') and specific outputs ('views and leads', 'the performance numbers PF Expert shows'), which cleanly separates it from property-finder_get_listing and list_listings. An agent knows exactly what it retrieves without opening the schema.

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?

Gives real usage context: call once per listing, keep the set small, and filter with list_listings first. It does not state when-not-to-use or name an alternative for aggregate/portfolio stats, but the operating guidance is concrete.

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