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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=false and destructiveHint=false, so the safety profile is fully covered by structured data. The description adds that the counts are limited to 'published' entities and that a freshness timestamp is returned, which is genuinely useful behavior beyond annotations, but nothing is said about scope (workspace-wide vs filtered) or recency semantics.

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?

A single sentence that front-loads the returned quantities and ends with the freshness signal, with no redundant restatement of the name or title. Nothing could be trimmed without losing information.

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 zero-parameter, non-destructive read tool with no output schema, the description carries the full burden of describing return values, and it does so by enumerating vendor/place/category counts plus a last-changed timestamp. An agent has everything needed to call it correctly and interpret the response.

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?

The tool takes zero parameters, so there is no parameter meaning to explain; the baseline of 4 applies. The description correctly introduces no phantom inputs, reinforcing that this is a parameterless aggregate call.

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 names a specific verb ('Get the number of') and enumerates the exact resources counted (published vendors, places, categories) plus a last-changed timestamp. This clearly distinguishes it from the sibling list_categories/list_places/search_listings tools, which return records rather than aggregate counts, though no sibling is named explicitly.

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?

Usage is only implied: an agent can infer this is the summary/count tool to call instead of listing and counting records itself. There is no explicit statement of when to prefer it, and no exclusions or prerequisites are given, which matters little here since the tool takes no parameters.

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