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

readOnlyHint=true already establishes this as a safe read. The description adds a genuinely useful behavioral fact not covered by annotations: the call is free. It does not, however, disclose anything about result count, ranking, or ordering of suggestions.

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 short sentences: the first defines the action, the second defines the return and gives an illustrative example. Zero filler, front-loaded with the core purpose.

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 simple two-parameter read tool with no output schema, the description covers purpose, return semantics, and cost. Minor gaps remain (how many suggestions, whether results are ranked), but nothing essential for correct invocation is missing.

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 description coverage is 100%, so both service_id and country are already documented with format and example values. The description adds no parameter-level detail beyond what the schema provides, so the baseline 3 applies.

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 verb+resource ('Suggest related services for a given service') and immediately clarifies the semantics of 'related' as complementary services commonly used together, with a concrete example. This is clearly distinct from siblings like search_services or get_catalog.

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 example ('after looking up a postcode, suggest demographics and income') implies a usage context — following a lookup to discover adjacent capabilities — but there is no explicit when-to-use/when-not guidance and no named alternative tool for the same need.

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