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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the agent knows this is a safe read against an external dataset. The description adds useful behavioral content by revealing that each topic is accompanied by in-force counts for Acts and regulations, which is not obvious from the name. It says nothing about whether all topics are returned at once or how large the result set is.

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?

Two sentences, front-loaded with what the tool returns before mentioning the optional filter; nothing is redundant. The second sentence is slightly telegraphic ('Optionally only those whose name has these words'), which costs a little clarity but not length.

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 one optional parameter, no output schema, and read-only annotations, the description is nearly sufficient: it describes the returned fields inline, which compensates for the missing output schema. Only the result-set shape (complete list vs paginated) is unaddressed, a minor gap at this complexity.

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% and the single query parameter is already documented with example values (housing, tax, employment). The description adds only that the match is word-based against the topic's name, which is marginal beyond the schema. Baseline 3 applies when the schema carries the semantics.

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+resource (listing topics) and even defines the domain term: topics are 'the official subject headings of legislation.gov.uk'. It also discloses what each entry carries, the number of Acts and regulations in force. It does not explicitly contrast itself with get_topic, but the singular sibling name makes the distinction inferable.

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: the optional filter is introduced with 'Optionally only those whose name has these words', which tells the agent that an unfiltered call is valid. There is no statement about when to prefer this over get_topic or search_laws, and no guidance on how to find a topic's identifier for a follow-up call.

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