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

With no annotations, the description carries the full burden, and it does disclose one important trait: the password is not returned. However, it omits whether the form is submitted (the schema has a `fields.submit` entry), what happens on failure, what permissions/state are required, and whether navigation occurs.

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, and the security-relevant note ("password is not returned") is placed where it will be read. Nothing redundant or padded.

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 4-parameter tool with a nested object, no output schema, no annotations, and 25% schema coverage, this is far too thin — the meaning of `fields` and `cdp_url` and the submit behavior are all left unexplained.

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 only 25% (only `identity_id` documented), and the description says nothing about `site`, `cdp_url`, or the nested `fields` object with username/password/submit — the reader cannot tell whether those are CSS selectors, field names, or literal values. It does not compensate for the coverage gap.

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 ("Type the saved username and password into the matching page over CDP") and clearly occupies the credential-filling slot among siblings like fill_code, get_email_code and open_magic_link. The phrase "matching page" is left undefined (matching which site? the `site` param presumably), which keeps it from a 5.

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?

There is no explicit when-to-use or when-not-to-use guidance, no mention of the prerequisite that a login must have been saved via save_login, and no routing versus fill_code/fill_email_code/restore_session. The agent must infer usage entirely from the verb.

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