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

Discloses a genuinely non-obvious behavior: with no account attached it returns an error result that *carries* the connection request, and the error is the delivery mechanism, not a failure. It also states idempotency consequences (calling again returns the same request) and the no-op case when an account is already attached, consistent with the readOnly/idempotent annotations.

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?

Purpose and triggers are front-loaded, and the error-as-request paragraph earns its length because it prevents a misread. It runs slightly long and repeats the `check_only` guidance already present in the schema, so it is efficient but not maximally tight.

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 one-parameter tool with an output schema and safety annotations, the definition covers everything an agent needs: the trigger conditions, the no-account error semantics, idempotent repeat behavior, and the set-vs-unset rule for `check_only`. Return-value detail is rightly left to the output schema.

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 100%, so `check_only` is already fully documented in the schema, including its default. The description largely restates that the grid sets it and that it should be left unset otherwise, adding only slight emphasis rather than new semantics. Baseline 3 is appropriate.

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 action and resource: it asks the host to run its own Pexafy account-connection flow. It implicitly separates itself from the four search/photo siblings, none of which deal with account state, and clarifies it is not a search tool.

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 explicit triggers (person asks to connect/link/sign in, or hits the account button, or wants more than the daily allowance) and an explicit exclusion ('It does not search, and searching does not require calling it'). It also spells out when to set versus leave unset `check_only`, leaving nothing to inference.

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