set_primary_email

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

Annotations already declare readOnlyHint=false and destructiveHint=true, so the mutation risk is known. The description usefully adds the authentication prerequisite, but it never explains the destructive consequence: what happens to the previously primary email address. That is the key behavioral fact an agent would want, so it adds some value without closing the loop.

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 purpose is front-loaded in one short sentence, followed by a compact prerequisites block. The ACCESS text is somewhat long for a one-parameter tool but every clause carries actionable information.

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 single-parameter mutation with annotations covering the safety profile and no output schema, the description covers authentication but omits the effect on the prior primary email and any confirmation/return behavior. Adequate but with a clear gap around the mutation's consequence.

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% and the schema itself is precise ('Email record ID to set as primary'), but the description describes the input loosely as 'an email address', which conflicts with the ID-based parameter and could lead an agent to pass an email string instead of a record ID. The description adds no clarifying syntax beyond the schema and introduces mild ambiguity.

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: 'Set an email address as the primary email for the account.' It is distinguishable from siblings like set_primary_phone and set_primary_profile by the 'email' resource, though it never names or contrasts those siblings explicitly.

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 ACCESS block gives actionable prerequisites (needs a Proof account; set PROOF_API_KEY or sign in via start_login, then call again), which is genuine usage guidance. However, it says nothing about when this tool is appropriate versus the other primary-setting siblings, so selection guidance is only implied.

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