Summarize correspondence history

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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered externally. The description adds that the result is a single aggregated object and that input is scoped to one contact/domain, but says nothing about how the limits or mutual exclusivity between contact and domain behave. A 3 is appropriate given annotations carry the primary behavioral burden.

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 tight sentences with zero waste; the purpose and scope are front-loaded before the disambiguating second sentence. Every clause earns its place.

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?

The existence of an output schema means return values need not be explained, and the disambiguation from siblings is strong. However, with 6 undocumented parameters and no mention of the date-range filters or limit defaults, the definition is only partially complete for the tool's input complexity.

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 0%, so the description must compensate for all 6 parameters. It only clarifies contact/domain (exactly one of a contact address or a domain) and leaves date_from, date_to, contacts_limit, and attachments_limit entirely undocumented, so most parameters gain no meaning beyond their bare names.

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 ('Return one aggregated correspondence-summary object') and scopes it precisely to 'exactly one contact address or one domain.' It explicitly distinguishes itself from the sibling message tools (mail_search, mail_show, mail_thread), so an agent can route correctly without opening a 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?

Gives an explicit when-not ('This is not a message search or thread tool') and names the alternatives with the condition that selects them ('use mail_search, mail_show, or mail_thread for individual messages'). The selection logic is fully inferable with no ambiguity.

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