add_chain_link

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

Annotations already declare destructiveHint=true, idempotentHint=false, readOnlyHint=false, so the safety profile is covered. The description adds one genuinely useful behavioral fact — that link_number is auto-incremented — but says nothing about ordering constraints, required chain state (e.g. paused vs active), or that repeated calls create distinct links (non-idempotent).

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, front-loaded with the action and followed by the one non-obvious side effect. No filler. Its brevity is the only reason it reads well; the content gap is a separate dimension.

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?

An output schema exists, so return values need no explanation, and annotations carry the safety profile. Still, for a destructive, non-idempotent mutation on a chain, the description omits prerequisite chain state and the effect on sibling links — leaving the agent to guess at operational context.

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?

The description mentions only link_number, which is not an input parameter at all; chain_id, session_type, started, and progress_markers are unaddressed in prose. The schema descriptions do carry per-field text, but with reported 0% coverage alignment the description should be compensating and is not.

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 states a specific verb and resource ("Add a new session link to a chain"), which is far more informative than the bare name. It distinguishes itself from complete_chain_link and branch_chain by implication, though it never names a sibling or clarifies what a 'session link' has to do with the surrounding chain vocabulary.

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?

No guidance on when to add a link versus completing, branching, or spawning a child chain — all adjacent sibling operations. The agent has to infer usage entirely from the tool name and the one-line purpose statement.

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