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

Annotations already declare idempotent, non-destructive, non-readonly behavior, so the bar is lower. The description still adds real context beyond them: 'Only supplied fields change' (partial-update semantics), 'tenant-scoped', and that stage changes are written to the audit history.

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?

Four tight sentences, front-loaded with the primary use case followed by the alternative-selection rule. No filler or restated schema.

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 mutation tool with no output schema and 12 loosely-described params, the description covers identification, partial-update behavior, scoping and audit side-effects. Remaining gap is per-field semantics, but nothing critical to 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?

With 12 params and only 50% schema description coverage, the description should compensate more. It clarifies the identifier choice (contact_id vs crm_lead_id) and the three concerns, but leaves many params (note, email, phone, company, headline, location, position, clear_deal_value) as a generic 'contact details' bucket.

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 (update) and resource (CRM lead) and enumerates the mutable concerns (stage, deal value, contact details). It also names the sibling alternatives, so the agent can distinguish it 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 routes the agent: 'For a single concern prefer set_deal_stage, update_contact or set_lead_fields.' This gives a clear when-to-use-this vs when-to-use-alternative rule, which is rare and valuable.

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