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

readOnlyHint=true already declares this as a safe read; the description adds only the GET /api/clients mapping, which is mild extra context. It does not disclose that results are truncated with no pagination (that fact lives only in the limit param schema), nor any rate-limit or auth behavior.

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 fragments with zero filler; the purpose is front-loaded and the REST endpoint is appended as supporting context. It is arguably terse given the schema's nuanced truncation behavior, but nothing 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?

With no output schema, the description does helpfully preview returned fields, which is appropriate for a simple read-only list. However, for a tool whose pagination model is non-standard (hard truncation at 500), the definition omits any behavioral summary an agent would want before calling it.

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 limit, where, active, and include are all fully documented in the schema itself. The description's parenthetical (id, name, contact details, active flag) describes returned fields rather than adding parameter meaning, so it does not exceed the baseline.

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 ('List clients') and names the fields returned (id, name, contact details, active flag), plus the underlying REST call. It is distinguishable from siblings like paymo_list_projects or paymo_list_invoices by the resource alone, though it does no explicit sibling differentiation.

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?

No guidance on when to use this versus paymo_get_company, paymo_list_projects, or other list_* tools, and no mention of how the active/where filters should be applied when choosing this tool. The agent must infer usage entirely from the name.

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