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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful context beyond that: page size (up to 100), the cursor round-trip for pagination, and the auth requirement ('Needs the user's Cotlet API key with access to this app'). It doesn't add much more, so a 4 rather than a 5.

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?

Effectively one dense paragraph with the core purpose front-loaded and each subsequent sentence adding a distinct capability (search, role filter, cross-tool IDs, pagination, auth). It is slightly overpacked, and the opening field list reads a bit like a data dump, but nothing is padding.

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?

There is no output schema, so describing the returned fields is essential and done here. Coupled with pagination limits, auth needs, search/filter semantics and cross-tool ID usage, an agent has everything needed to call this correctly.

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 four parameters are already documented, setting a baseline of 3. The description adds value by explaining how cursor is consumed ('pass next_cursor back as cursor') and what role filtering is for, and it maps the contact_id output field to downstream parameters in create_invoice/create_purchase, which is meaning beyond the input schema.

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 and resource ('Lists the contacts of the company') and immediately clarifies that contacts encompass both customers and suppliers, plus the fields returned (ID, name, org number, email, customer/supplier number). An agent can distinguish this read-list tool from the sibling fiken_create_contact without opening any 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?

Explicitly says when to use it: search by name or organisation number to check existence before creating a contact, and filter by role to isolate customers or suppliers. It also routes cross-tool usage ('Use contact_id as customer_id in create_invoice and as supplier_id in create_purchase'), naming the sibling tools that consume the output.

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