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

Annotations already flag write/destructive/idempotent, and the description adds non-obvious behavior the agent cannot get elsewhere: partial-update semantics and the crucial warning that passing sales_accounts replaces the contact's associated companies. That is exactly the kind of 'what gets overwritten' context the annotations do not supply.

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?

Front-loaded 'WRITE:' marker, then the core semantics, then the endpoint. One compact sentence plus a reference; no filler.

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?

Covers mutation type, partial-update behavior, the nested sales_accounts caveat, and the HTTP surface for an 18-parameter tool with no output schema. Minor gaps: it doesn't state what happens with an invalid contact_id or how clearing a field works.

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 baseline is 3; the description earns above that by explaining the destructive replacement behavior of sales_accounts, which the schema only describes structurally. Other parameters rely on the schema, which is acceptable given full coverage.

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 ('change fields') and resource ('an existing contact'), which cleanly separates it from freshsales_create_contact (new) and from update_account/update_deal by resource. The PUT /contacts/{id} line confirms the target.

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?

Clear that this is for modifying an existing contact and that updates are partial ('only the fields you pass are changed'). It does not name alternatives or say when not to use it (e.g. use create_contact for new records), so it stops short of explicit routing.

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