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

With no annotations, the description carries the full burden. It usefully discloses that this is a mobile API login and that it yields session cookies, which is the key side effect an agent needs. It says nothing about failure behavior on bad credentials, whether existing sessions are invalidated, credential handling, or rate limiting — meaningful gaps for a session-creating mutation.

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 short sentences, zero filler, with the action and target front-loaded and the return value stated second. Nothing here could be cut without losing 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 three-parameter login with no output schema, the description covers the action, the auth method, and the returned artifact, which is the essential shape. Missing are error/credential-failure semantics and session lifetime, which an agent would need to sequence subsequent calls safely.

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 all three parameters are already documented in the schema, establishing a baseline of 3. The description corroborates the two required credentials ('email and password') but adds nothing about format, and the third parameter, notification_message, is not mentioned at all.

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 (log in), resource (Jiji Nigeria account), mechanism (email and password via mobile API), and outcome (session cookies). This is inherently distinguishable from the only opposite sibling, logout, without opening either 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?

The phrase 'for authenticated pipelines' implies this is a prerequisite for other authenticated calls, which is useful implied usage. However, it never states when not to call it (e.g. when a valid session already exists), nor does it name any alternative or reference the logout sibling for session lifecycle.

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