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

With no annotations, the description carries the full burden. It discloses that the tool returns a list of tools to call (not data itself), mentions the rendering_contract and render fields, and warns about default behavior if client_capabilities is omitted. However, it does not specify any side effects or potential limitations.

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?

The description is somewhat lengthy but every sentence adds value. It fronts the purpose and usage, then covers parameters and response fields. Could be slightly more concise, but overall well-structured.

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?

Given no output schema, the description explains return fields (rendering_contract, render) and parameter details well. It provides enough context for an agent to use the tool correctly, though it could mention if there are any error conditions or rate limits.

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 baseline is 3. The description adds value beyond schema by explaining that timezone is passed through to called tools, client_capabilities tiers mirror the rendering_contract ladder, and expected_contract_version is for version comparison. This enriches parameter understanding.

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?

The description explicitly states it returns today's date and a list of tools to call in parallel for a morning briefing. It distinguishes itself from siblings by noting it does not fetch data itself, making the purpose clear and unique.

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?

The description provides clear usage instructions: use at the start of every session or when the user says 'start my day', 'catch me up', or similar. It also tells the user to read specific response fields (rendering_contract, render) before composing output.

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